A new Grocery Outlet store opened last year in South San Francisco, and I've had the opportunity to shop there a few times. They prices are generally pretty good, although selection can be limited (and be mindful of expiration dates -- things are often being sold just days before the sell by dates).
The store saves money by buying in bulk, overstock, etc. Another way it saves money is by having export-marked food items whose order has apparently fallen through. I recently bought some Welch's grape juice marked for overseas sale, for example.
But the most apparent example was when I last month bought two cans of Spam (yes, I enjoy Spam in non-emailed form).
One (above, right) had markings in an Asian language (possibly Japanese). The other (above left) had what appeared to be Arabic markings and the warning "Pork — Not for Muslims." I'm not sure where that latter can is intended to be sold — maybe India because of the English markings, or Saudi Arabia for the Filipino guest workers (Spam is apparently popular in the Philippines).
Some may worry about "export-quality" items, but I think buying items such as the above is an interesting look into how the outside world sees American product.
