itch.io's cut does not include the fee added by the payment processor. Payment processor fees are applied per transaction, not per payout. So if you sold 50 items for 1 dollar then the 30 cents + 2.9% payment processor fee would be a significant portion of the revenue, about 50 * 0.33 = $16.50
We recommend charging as much as you feel comfortable with to reduce the fee from the payment processor. For example, if you sold 10 units for 5 dollars, the fee would about 10 * 0.45 = $4.50