Many markets on Polymarket, especially "related markets" like spreads or player props, have very low liquidity, which can cause issues with certain estimates you may see while trading.
Average price estimates and payout estimates are calculated based on the best possible price available on the order book. These estimates do not take into account fees or low order book liquidity. When you trade on markets with fees or low liquidity, it may not be possible to fill your entire order at the best price available (slippage).
These factors are only taken into consideration when you open order review window, since we need to know how much you intend to trade before calculating the most accurate estimates. As a result, on markets with low liquidity, you may see drastic differences in estimates between the order entry box and the review window.
Additionally, since we currently only offer market orders, the actual price may still vary slightly once you place your order. You'll see the actual price and number of contracts purchased on the confirmation screen. In the event the price changes drastically between the time you place your order and the time it is matched, we will reject the order for safety.
We're working to make these situations clearer in the app, but keep in mind that trading low liquidity markets carries higher risk.