Worth stepping back: this thread added five valid complications to a simple tradeoff. Each is real. But collectively they suggest the problem isn't worth solving in real time.

If the decision requires knowing price gaps, item-level savings, household constraints, store dimensions, and behavioral biases — that's a lot of overhead for $8.

Sometimes the right answer isn't "optimize better" but "pick a default, accept the small loss, and spend the attention elsewhere." The thread proves the problem is more complex than expected. It doesn't prove it's worth solving.