The interface can hide that difference. A “60% chance” contract and decimal odds of 1.67 describe roughly the same implied probability before fees and margin, yet the customer may be trading with another participant in one product and betting against an operator in another.
Three products that can look alike
| Product | Who sets or forms the price? | Who takes the other side? | How the platform is paid |
|---|---|---|---|
| Fixed-odds sportsbook | The operator posts and moves odds using trading, risk and market inputs | The sportsbook is generally the counterparty | Margin built into prices; product-specific charges may also apply |
| Betting exchange | Customers post offers; the order book and matching process form the available odds | Another customer, with the exchange facilitating the match | Usually commission or a disclosed charge |
| Event-contract prediction market | Participants submit bids and offers for Yes/No contracts under venue rules | Another participant takes the complementary position; clearing and settlement depend on the venue | Transaction fees defined by the venue’s schedule |
This table describes common structures, not every contract. A sportsbook can use an exchange for risk management. A prediction platform may use market makers to improve liquidity. Legal classifications vary by jurisdiction, so product mechanics do not by themselves answer whether a platform may serve a particular person.
One event, three price experiences
Imagine an event with two mutually exclusive outcomes: North wins or North does not win.
A sportsbook might offer decimal odds of 1.67 on North. A 100 stake would return 167 including the stake if North wins, and lose 100 if it does not. The displayed odds imply about 59.9% before accounting for the bookmaker’s margin and the prices on other outcomes.
On an exchange, a customer might ask to back North at 1.67. Another participant must be willing to lay that outcome at a compatible price. The exchange matches them. The gross win is then affected by the exchange’s commission rules.
On an event-contract market, a Yes contract might trade at $0.60 and settle at $1 if North wins or $0 if it does not. Buying 100 contracts costs $60 before fees and produces $100 at correct Yes settlement, a $40 gross gain. A No buyer holds the complementary side. Kalshi's current help centre and Polymarket's product-specific documentation are examples of why the fee schedule must be read alongside the contract. Kalshi fees Polymarket US fees
Those examples are economically related, but they are not fee-equivalent. A contract venue may calculate fees using price, quantity and a coefficient. The coefficient is not simply a percentage of the full amount paid. A sportsbook’s margin is embedded in the set of odds rather than shown as a separate ticket fee.
Who makes the price?
At a sportsbook, traders and automated systems quote the odds. They consider probability estimates, market prices, liabilities and limits. The operator can change or suspend a market. A customer decides whether to accept the displayed price.
In an order-book market, participants publish intentions to buy or sell. A market maker may quote both sides, but other participants can improve the price. The visible price is therefore a market state, not a promise that any size can execute at that level. A thin order book can move sharply when a large order arrives.
The price of a Yes contract is often read as a probability. That is a useful shorthand, but it is still a traded price. Fees, liquidity, participant constraints, resolution risk and the time value of locked funds can separate it from a pure forecast.
Counterparty and credit structure
The counterparty question tells the reader where risk sits.
In fixed-odds betting, the operator writes the ticket and owes the winning return under its rules. Regulation, segregation requirements and company controls shape how customer funds are handled.
On an exchange or contract market, participants take complementary positions while the venue matches, clears and settles them. The venue still matters. Its rulebook defines eligible orders, collateral, market cancellation, dispute procedures and the evidence used at settlement.
“Peer to peer” does not mean “platform free.” The platform controls admission and contract design, and it can collect fees even when it does not hold an economic opinion on the event.
Settlement is a product feature
A sports bet normally settles from the result and the bookmaker’s house rules. Those rules cover questions such as postponements, dead heats or abandoned events.
An event contract settles against a written condition. The useful reading is not just the market title but the resolution source, cutoff, definitions and edge cases. “Will candidate X win?” can mean a certified election result, an inauguration, or another specified event. Two markets with similar headlines can settle differently. Polymarket International's current fee page also shows that even the charging model can vary by category. Polymarket International fees
That rule risk is distinct from forecasting risk. A trader can predict the real-world event correctly and still misunderstand the contract’s resolution language.
Liquidity changes the practical price
A headline quote is not enough to compare execution. A customer should look at the spread between the best bid and offer, the depth available at each price, order type and the fee schedule. A market showing 60 may have only a small quantity available before the next seller asks 63.
Sportsbooks express a related constraint through limits and offered prices. The operator may accept a small wager at one price and move the line or restrict the amount. Neither interface guarantees that a large position can be placed at the first number shown.
Regulation and access
The legal route differs by market and place. A sportsbook may operate under a state or national gambling licence. A US event-contract venue may be regulated through the derivatives framework. An international prediction platform may use another structure and restrict access from specified locations.
That means “prediction markets are legal” and “sports betting is legal” are both incomplete statements. The platform, contract, user location and current rules matter. A comparison page should state the product and geography being discussed, as our Kalshi and Polymarket comparison does.
A useful way to choose the right comparison
Ask four questions before comparing prices:
What exactly triggers settlement?
Who takes the other side and holds the collateral?
What fee or margin applies at the intended size and price?
Is this product available to this participant in this location?
Once those are answered, the apparent similarity becomes manageable. Sportsbooks, exchanges and prediction markets can all price uncertainty. They do it through different contracts and different relationships between the participant, the venue and the other side.
