Cart

The cart is the second offer.

Average order value moves after the first add. The product page can introduce a pair or a quantity break. The cart decides whether that offer is still visible.

A goal the shopper can see

A free-shipping bar works when the threshold is close to a typical order and the remaining amount updates as the cart changes. A gift or a discount at the same threshold is a second reason to add, not a replacement for a clear price.

Bundles on the product, not only in the cart

Frequently bought together and quantity breaks belong where the shopper is still choosing the first item. If the only offer appears after they have already decided to leave, it is late.

Drawer or page

A cart drawer keeps the product in view. A full cart page is fine when the offer and the shipping goal are on that page. What fails is an add that goes nowhere, or a drawer that never shows the new line.

Run both the product and the cart through the CRO audit.