[xp84]

I seem to remember Jet.com might have had something kind of like this, except I think it was defaulted to "allow returns" and they would offer you, on each line item, to for instance "Save $0.37 by waiving returns."

Jet also had a very neat logistics-driven feature where if you bought more things that came from the same warehouse they passed some of that savings onto you. So once you had in your cart, say, a box of paper towels, you might save $1.50 off of a box of crackers that they knew they could throw into the same box.

Marc Lore is clever and I was sad to see Jet.com go (though not sad for him since I think it was another great exit)