Line shopping: how comparing odds changes the price you pay

The same bet can cost different amounts at different licensed bookmakers & prediction markets, & fees, stake size & account limits all shape the real price.

Why price matters as much as the pick

Line shopping means comparing the price offered for the same bet at several bookmakers or platforms before deciding where, or whether, to place it. The price matters because it sets the break-even rate: the share of bets that must win for a bettor to neither gain nor lose over time.

Prices here are American odds, such as +100, -110 or +200, where the number sets how much a winning bet returns. According to Covers, a bet at +100 normally needs to win 50% of the time to break even, while a bet at -110 needs 52.4%. At +200 the standard break-even rate is 33.3%.

That gap comes from the price itself, before any view of the game enters the picture. Two bettors who pick winners at the same rate face different break-even targets if one pays a worse price for the same outcome.

Where prices differ

Covers reported a comparison by Citizens of pricing at Kalshi, a prediction market operator, against the sportsbooks FanDuel & DraftKings during Week 1 of the 2026 NFL season. Citizens measured implied vig, the margin built into a set of prices, & found it was 4.32% at Kalshi, 4.44% at FanDuel & 4.51% at DraftKings, according to Covers.

Citizens tracked pregame prices in moneyline markets (a bet on who wins) & over/under markets (a bet on whether the total score lands above or below a line) on the Friday before the first Sunday slate. Across 28 data points, Kalshi’s implied vig was 3% lower than FanDuel’s & 4% lower than DraftKings’.

The order was different a season earlier. Citizens said Kalshi’s implied vig during the 2025 NFL season was 4.84%, behind FanDuel’s 4.42% & DraftKings’ 4.48%, & attributed the change to increased trading volume, market participation & competition among liquidity providers.

The ranking flipped again for multi-leg bets. Citizens found the two sportsbooks priced parlays better than Kalshi priced its equivalent combos, with Kalshi’s implied vig 8% worse before transaction fees, & said it was watching whether a combo market making fee Kalshi introduced in August would affect spreads.

The comparison suggests that no single venue in it was cheapest for every type of bet. A price check on a single game & a price check on a parlay can point to different operators.

Hidden costs

The quoted odds are not always the full cost. Covers reported that FanDuel reinstated a 50-cent charge on qualifying wagers in Illinois, passing along the state’s per-bet tax, which first took effect on 1 September 2025, with Illinois bettors posting about the reinstated fee on 6 October 2026.

According to Covers, Illinois lawmakers approved a per-bet tax of 25 cents on the first 20 million wagers per operator & 50 cents on all additional tickets. FanDuel is available in 24 states & Washington, D.C., & bettors in 23 of those markets face no additional per-bet fee.

The fee weighs most on small stakes. On a $1 bet, Covers calculates the break-even rate rises to 66.7% at +100, 71% at -110 & 40% at +200; on a $10 bet the figures are 51.3%, 53.8% & 33.9%.

The charge does not apply to a parlay worth at least $10, a straight bet worth at least $25 or a wager made with a bonus bet. Covers also notes that DraftKings employs a per-bet fee in Illinois.

Moving money in & out has its own costs. Kalshi’s fee schedule lists no fee on ACH bank transfers, a maximum fee of 2% on card deposits & the right to charge between 0% & 2% on all payment rails.

Polymarket says it charges no fees to deposit or withdraw USDC, the currency its fees are calculated in, though intermediaries such as Coinbase or MoonPay may charge their own.

Compare only among licensed operators

A price comparison is only meaningful among operators licensed where the bettor is. The UK Gambling Commission publishes a public register where licensed gambling businesses, personal licences, regulatory actions & licensed premises can be searched & downloaded.

Regulators act against unlicensed operators. On 28 April 2025, Legal Sports Report reported that the Michigan Gaming Control Board had sent cease-&-desist orders to SportsBetting.ag & BetOnline.ag, both based in Panama & unlicensed in the state.

The board found the two sportsbooks in violation of the Lawful Internet Gaming Act, the Gaming Control & Revenue Act & the Michigan Penal Code, & said it would take further legal action if they did not cease operations in the state within 14 days. It had sent more than 40 cease-&-desist letters to offshore & unlicensed operators in the preceding year.

“We encourage residents to only engage with licensed & regulated online platforms for a safe & fair gaming experience,” said Henry Williams, the board’s executive director.

What the research shows

A paper titled Beating the bookies with their own numbers tested a strategy built on publicly available prices rather than a forecasting model. The authors used the probability information implicit in the odds available across the football betting market to find bets with mispriced odds.

They report that the strategy was profitable in a 10-year historical simulation using closing odds (the final prices before an event), a 6-month simulation using minute-to-minute odds & a 5-month period of staking real money. The authors made their code, data & models publicly available.

They conclude that the football betting market they studied is inefficient & that bookmakers could be beaten across thousands of games in both simulated & real-life betting.

The catch: account limits

The same paper describes what happened when the strategy worked. According to the authors, the sports gambling industry compensates for these market inefficiencies “with discriminatory practices against successful clients”, & they give a detailed account of their own betting experience to illustrate it.

The practical point is that a price shown on a screen is not always a price a given account can take. An operator that treats an account as too successful may not offer it the same terms as other customers.

Prediction markets as another price

Prediction markets charge trading fees by formula rather than building all of their margin into the odds. Kalshi’s fee schedule, effective from 7 July 2026, sets the general fee on orders that are immediately matched at 0.07 multiplied by the number of contracts, the contract price & one minus the price, rounded up.

Kalshi’s General Trading Fees Table, which applies that general 0.07 formula, lists $1.75 in fees for 100 contracts priced at 50 cents, against $0.63 for 100 contracts at 10 or 90 cents. Resting orders, which wait on the order book rather than matching at once, carry a separate maker fee of 0.0175 under the same formula, with a default multiplier of 0 unless a market says otherwise.

Polymarket’s fee documentation says only takers, who fill existing orders, pay fees; makers are never charged. Its fee is symmetric around 50% probability, peaking at $1.75 per 100 shares at that point, & geopolitical & world events markets are fee-free.

These platforms sit in a contested regulatory space. Citizens describes retail customers choosing prediction markets in states with legal sports betting, while Legal Sports Report reported in April 2025 that the Michigan Gaming Control Board was also investigating sports prediction markets. Williams said that “many of these unlicensed platforms are often accessible to individuals as young as 18, in stark contrast to Michigan’s 21+ age requirement for legal sports betting.”

Comparing prices like for like

A price comparison based on the sources above involves several checks. One is whether each operator is licensed where the bettor is, which regulators’ own records, such as the UK Gambling Commission’s register, show.

Another is the quoted price & its break-even rate, compared like for like: a single bet against a single bet, a parlay against a parlay or combo, since Citizens found the rankings differed between the two.

A third is every cost outside the odds: per-bet fees such as FanDuel’s 50-cent charge in Illinois & the stake thresholds that remove it, trading fees on prediction markets, & deposit or withdrawal fees. Only after those are added does one price become directly comparable with another.

Questions

What is line shopping?

It is comparing the price of the same bet across several operators. The price sets the break-even rate, which Covers puts at 50% for a bet at +100 & 52.4% for a bet at -110.

Were prediction markets cheaper than sportsbooks?

In Citizens’ Week 1 2026 NFL comparison, Kalshi’s implied vig was 4.32% against 4.44% at FanDuel & 4.51% at DraftKings. The sportsbooks priced parlays better than Kalshi priced combos.

How does the Illinois per-bet fee change the maths?

According to Covers, FanDuel’s 50-cent charge raises the break-even rate on a $1 bet at +100 from 50% to 66.7%. The effect shrinks as stakes rise, & the fee does not apply to straight bets of at least $25, parlays of at least $10 or bonus-bet wagers.

How can I check whether an operator is licensed?

In the UK, the Gambling Commission’s public register lists licensed businesses & regulatory actions. In Michigan, the Gaming Control Board has sent cease-&-desist orders to unlicensed operators including SportsBetting.ag & BetOnline.ag.

Do bookmakers restrict winning accounts?

The authors of Beating the bookies with their own numbers say the industry responds to successful clients with discriminatory practices, & describe their own experience as an example.

Sources

• covers.com
• covers.com
• arxiv.org
• kalshi.com
• docs.polymarket.com
• gamblingcommission.gov.uk
• legalsportsreport.com

Sources checked 9 October 2026. Information only. 18+.