No MLB props are priced at both Kalshi and Polymarket at this moment. Prices repopulate as each slate's boards open.
How they differ
Two exchanges, no sportsbook margin on either side, and a real difference in how they charge. Kalshi's fee is a curve that peaks on near-even markets; Polymarket's is a flat fraction of a percent, which tends to make it cheaper in the middle of the price range. Kalshi lists more sports markets and carries deeper coverage; Polymarket's depth is concentrated on the games people are trading. Where both price the same prop, the number below is which one is currently ahead.
Where Kalshi is cheaper
Kalshi is not currently the better price on any MLB props both venues list.
How each one charges
- Kalshi
- Kalshi is a CFTC-regulated exchange. Every contract settles at $1 or $0, so a 42¢ quote is a 42% implied probability with no sportsbook margin layered on top.
- Kalshi charges a per-contract trading fee instead of building a margin into the line. The fee is a curve, not a flat rake: it peaks at roughly 1.75¢ on a contract priced near 50¢ and shrinks toward zero at both extremes, and maker fees are a quarter of taker fees.
- Kalshi lists player markets as "X or more" yes/no contracts rather than as an over/under line, so BeatVig converts each contract to the equivalent over price before comparing it to a sportsbook number.
- Polymarket
- Polymarket is an order-book market: the price is whatever two traders agree on, and a share that settles at $1 quotes as a probability directly.
- Polymarket's taker fee is a fraction of a percent, which makes its headline quote very close to the all-in cost and often the cheapest of the exchanges in the middle of the price range.
- Polymarket runs deep liquidity on headline games and much thinner books on the rest of the slate, and its player-prop coverage is still filling in — check the size behind a quote, not just the quote.
Kalshi vs Polymarket FAQ
Is Kalshi cheaper than Polymarket?
It depends on the prop, which is why this page measures it continuously rather than quoting a single number. Neither venue is cheaper on everything, and the answer changes as both boards move.
How do you compare a Kalshi price to a Polymarket price?
Every quote from both venues is converted to the implied probability of the same outcome, so a contract price and an American price become the same unit. The cheaper venue is the one implying the lower probability for the side you want.
What does Kalshi charge?
Kalshi charges a per-contract trading fee instead of building a margin into the line. The fee is a curve, not a flat rake: it peaks at roughly 1.75¢ on a contract priced near 50¢ and shrinks toward zero at both extremes, and maker fees are a quarter of taker fees.
What does Polymarket charge?
Polymarket's taker fee is a fraction of a percent, which makes its headline quote very close to the all-in cost and often the cheapest of the exchanges in the middle of the price range.
How often does this comparison update?
It is computed from the live board every time the page loads, so it reflects the prices both venues are showing at that moment rather than a snapshot taken on an earlier day.