Polynomial trade charges 0 fees on standard orders. You'll get the exact same price trading through Polynomial trade as what you'd get trading through the perps v2 contracts directly.
Keeper deposit: Dynamic fee given to the keeper bots to execute the trade (from 0$ to 10$)
Fees: 2/6-10 bps based on the market skew.
Apart from the standard fees from Synthetix, Polynomial charges around $1.25 fixed cost + 3bps of notional size is the total fee for limit/stop orders.
Keeper deposit: Dynamic fee given to the keeper bots to execute the trade (from 0$ to 10$).
Fees: 2/6-10 bps based on the market skew.
Limit keeper deposit (Charged by Polynomial): Fixed fee around $1.25 (depends no the network congestion).
Fees: 3bps of notional size.
The fees are only charged when the order is executed finally.