Extra Product Options

Sell the extras that cannot be variants. Gift wrap, an engraved name, an uploaded logo, a delivery date — put them on the product page as fields and charge for the ones a shopper picks. Charge a fixed amount or a percentage, per item or once for the order. Show a field only when an earlier answer calls for it. Group a long form into sections or tabs. The price is never taken from the page. Checkout works it out again from what was chosen, so an edited page cannot change what anyone pays.