> Ok, so 100 people can all drive to the store, or one delivery truck can drive to everyone's house.

Whether you see that statement and read it as "obviously the delivery truck is better" or "obviously, going myself is better" is going to be primarily based on how far away from Costco you live, and how much you buy when you go.

I live a bit more than a mile away from Costco. I often buy 25-60 items, for each of the about weekly trips. There's enough large items that a normal delivery truck that could safely navigate and stop often in residential areas would have no change of fitting 100 people's purchases into it in a way to be easily offloaded (just the toilet paper and paper toweling would take up significant space). It's much less wasteful on almost all metrics for me to go to Costco. That's before we get into the fact that most of what I'm buying is produce and other food stuffs I wouldn't want shipped for worry they would spend longer than I wanted out of refrigeration.

If I lived an hour away that calculation turns out entirely differently, at least as long as there's enough people close by with purchases to gain efficiencies of travel.