Costco serves my needs as primary purchaser of the household by providing the right products at the right place at the right time and most importantly, at the right price! In addition, as our taste matured, I think Costco followed their customers by seeking what demand and providing it.
One example is their expanded selection on organic products. For a long time, they have a remarkable price on organic milk. Now, they carry Stonyfield Farms and other organic frozen foods, prepared meals (sorry, brand names elude me right now). We all know that organic food can be pricey, so any discount provided by leveraging bulk purchases is ok with me.
One stop shopping convenience. If you are having a party or a picnic, this is the place to be! When at Costco, I usually get my gas' worth off my fuel efficient car and do the following:
1) Buy tires. Tires go on sale in the springtime (check the coupon book mailers). The tires are nitrogen inflated, Costco offers free tire rotations and carries a warranty on the tires. The tires are installed while you shop.
2) Pick-up disposable contacts. Their price beats out 1-800 contacts.
3) Order digital prints. At $.13 a print, they set a standard on quality prints.
4) Largest selection of wine or beer (good for parties).
5) Produce. The bell peppers are cheaper here. They have 6 for $4.99 (2 of green, red and yellow).
6) Bakery. The carrot cakes, croissants and those muffins! The chocolate 2 bites are worth fighting for!
7) Dry goods. I stock up on sundries (ie paper towels, pet food) and cut down the total shopping trips during the year.
There are other services that I just don't have the time for, but is available when I need it. For example furniture, a kitchen faucet, a piano, books, apparel & shoes, garden plants, office supplies & furniture, travel services.
Costco takes American Express, ATM debit cards, cash and checks. They have a wonderful return policy and Customer Service is very non-threatening.
One downfall, certain locations get crowded, especially on weekends. I try to go on a Wednesday or a weeknight.