The Cost of Loyalty Index

Every widely-cited sportsbook margin number is realized hold — revenue over handle, inflated by parlays. This is different: we measured the quoted prices themselves, live, across every major US sportsbook, and put a dollar figure on what betting at only one book costs you.

Dollars lost per $1,000 wagered, by book

The cost of loyalty is the expected value a bettor gives up by taking a book's price instead of the best price available at any major regulated US book at the same moment, on the same outcome and the same line — averaged over every market we sampled and expressed per $1,000 staked. Zero means the book was, on average, the best-priced option; it does not mean betting there is profitable.

Quoted hold: regulated books vs exchanges

Across the twelve regulated US books, median quoted hold on mainline markets ran from 4.71% to 6.94% — the big national brands cluster tightly at 4.7–4.9%, with the sweeps-style and newer entrants (Fliff, ReBet) pricing far wider. The offshore books we tracked sat in the same band as the majors (3.63%–4.72%). The betting exchanges and prediction markets were an order of magnitude cheaper: Kalshi quoted a median 1.97%, Novig 1.92%, ProphetX 1.62%, Polymarket 1.14%, and peer-to-peer BetOpenly effectively zero. A regulated-book bettor is paying roughly two to four times the margin an exchange user pays before either of them picks a side.

Note that DraftKings illustrates why quoted hold alone understates the story: its median hold (4.71%) ties for the sharpest among regulated books, yet its cost of loyalty ($33.58) is the highest of the big four. A book can price a thin margin overall while still sitting on the wrong side of the market's best price on the outcomes that matter — hold measures the book against itself; cost of loyalty measures it against everyone else.

Methodology

• Data. Live pre-game odds boards (moneyline, spread, total) captured three times daily across 22 sports from The Odds API, covering every major regulated US sportsbook plus offshore books and betting exchanges. 64 snapshots between July 4 and July 25, 2026: 475,192 book-market boards, just over one million individual prices, and 13,707 event-markets scored against a same-snapshot Pinnacle baseline.
• Quoted hold. For each book-market, the sum of implied probabilities (1 ÷ decimal odds) across all outcomes, minus one. We report the median per book. This is the margin the book itself prices in — independent of what bettors choose to bet. See our hold calculator for the arithmetic on any single market.
• Fair probabilities. Pinnacle's board for the same event and market, devigged multiplicatively (implied probabilities normalized to sum to 1) — the standard sharp baseline. Markets without a Pinnacle quote are excluded. See no-vig fair odds and devigging methods.
• Cost of loyalty. For each outcome, each book's expected value per dollar is (fair probability × decimal odds) − 1. A book's loyalty cost is the average gap between the best EV among regulated US books quoting that exact outcome and line, and its own EV — times $1,000. Outcomes are matched on name and point: a −2.5 spread is never compared to a −3.
• What this is not. Not realized hold, not a win-rate claim, not promo-adjusted. It measures posted prices only. Boosts, bonuses, and limits are outside its scope.

Download the data

The full per-book table is free to use with attribution to Iron Marker (ironmarker.com). For questions about the data or custom cuts, email [email protected].

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Iron Marker is an independent analytics tool, not a sportsbook, and is not affiliated with any operator named above. Figures describe posted odds during the sampling window and will drift as books re-price. This page is educational and not betting or financial advice. Must be 21+ (age varies by state). Problem gambling? Call 1-800-GAMBLER.