@nathan.perdriau: Most brands optimise their up-sells around margin. That's the wrong variable. What you're actually solving for is incremental contribution profit per order. The formula is simple: take rate x average order value x gross margin percentage. Three things that matter here: 1. Take rate is the multiplier. A low-margin product with a 20% take rate will almost always beat a high-margin product at 10%. 2. The order is already locked in. This is pure incremental profit with zero acquisition cost attached to it. 3. A $2.50 CP lift on a $20 acquisition base is a 12%+ improvement in unit economics. That moves your viable CAC ceiling. Push the most congruent offer, not the highest-margin one. Full stop.