Costco is a good place to buy in bulk, if you need to buy in bulk (have a big family, kidnapped a few people and keeping them for a ransom, hoping to gain some weight to qualify for disability payments, etc) But, if you come here as a single person, you're really just buying too much of something you wont really be able to finish.
(Unless its Nutella - who can't finish a huge container of that chocolate gold??)
Prices are decent, as you're buying in bulk - but again, it's only good if your buying things you need. Basics. If you're like me and enjoy buying new things, you're going to spend a lot for a lot of something, that you may not like a lot.
Parking can be a little hectic - so either come early or NOT on a weekend. it seems to be a lot of families outtings for some reason.
Bottom line - for families to buy their basics, it's a great stop. Otherwise, just head over to some smaller grocery store