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.

• 28 field types: swatches, image tiles, uploads, dates, sliders, text limits
• Charge a fixed amount, a percentage, or a one-off fee for the whole order
• Show a field, or a whole section, only when an earlier answer calls for it
• Add-ons become real products on the order, with their own stock
• Add-ons become real products on the order, with their own stock