> Assuming the "economy" pack is the only offer you visit a distinct store for and the good is perishable (so that stockpiling doesn't work), then it might be cheaper if you factor in the time you need to reach said store, shop there and get back home into the "cost".

I'm actually referring to same-store, same-time prices when neither the economy nor the smaller pack is specially discounted, so the travel, etc., cost is the same.

Stockpiling/perishability doesn't seem relevant in any way that favors economy packs -- an economy pack is either a larger single sealed pack (in which case, with most perishable goods -- which go bad faster once opened -- is strictly more problematic than stockpiling smaller packages with the same aggregate contents) or is itself an aggregate of smaller packages (in which case, its equivalent to stockpiling smaller packages.)

The only place I can see the convenience issue you raise being a factor is if one store only sells the economy pack and another store sells the smaller pack, and there is a convenience difference between the two stores. Then, there is a premium for the convenience of the store. But that kind of different-store scenario is not what I'm referring to.