A price comparison needs the same fee model

Two market prices look a few cents apart. Before calling that a gap, make sure the comparison uses the same side, size, and fee assumptions.

A headline quote is not the same thing as the net result you can execute.

Put both trades on one worksheet

Record side, quantity, available levels, spread, fee estimate, and expected payout for each market. Use the same timestamp and the same unit for both calculations.

A small order may fit at the top of the book while a larger order walks through several levels. The comparison changes with size.

Compare net outcomes

Subtract the costs that belong to each path before judging the difference. Include the fee model, expected fill, and any capital that stays locked until settlement.

If one quote is gross and the other is net, the apparent edge is a spreadsheet error rather than a market signal.

Recheck when the book moves

Save the calculation with its timestamp and refresh it before acting. A quote that survives only in a stale snapshot is not an executable comparison.

The useful question is not which price is lower. It is which complete trade leaves the better net outcome after the same assumptions are applied to both sides.

Further reading: Prices and order books · Resolution rules · Current fees.

Explore the markets: Open Polymarket (referral link).