Not the hostel in Amsterdam
If you live near a Costco, are a member, and shop there regularly, this post is not for you. Go back to your oversized and happy life.
If you are missing one of those conditions, you may be interested in the Flying Pig delivery service.
I've been a customer for over ten years now, and overall I am pretty happy with the service. The Flying Pig has always treated me well, and has regularly supplied me with coffee, frozen fruit, meat, Christmas turkeys (before I discovered The Meat Guy), and bread products. On rare occasions when we've had a problem, they always dealt with it quickly and satisfactorily.
So what is the Flying Pig? It's basically a service where people will go to Costco, buy stuff for you, and ship it to you.
The main advantage is convenience. You don't need to go to Costco or live near one, and you don't need to be a member.
The main disadvantage is cost. The Flying Pig increases the price of everything on their website (I think by 20-30%) over the Costco price, and also charges for delivery. I presume they don't feature everything you might find in Costco on their site either, which is probably a mixed blessing (no random extra purchases on impulse).
Basically the only thing I need from Costco is coffee beans. I get the Kirkland Starbucks Espresso Roast 1-kg bags to fuel my 5-cup a day habit.
Last year a Costco opened about fifteen minutes' drive from my house. I haven't been there yet, but I'm considering it. The markup and shipping on a big coffee order would probably pay for my membership. On the other hand, I would probably buy several times that in random unnecessary items that then won't fit in my fridge.
If you don't live near a Costco, though, you might want to take a look at The Flying Pig. If you're happy paying their prices the service should satisfy you.
Anyone else a customer? How have you found the service so far?