[robertskmiles]

> I would be a bit worried to eat one that cost over 10x less and the seller was still able to make a profit.

A lot of supermarkets, at least in the UK, sell various basic foodstuffs as loss leaders[1], so they are making a significant loss on each one they sell. They do this to get you into the shop, in the hopes that you'll buy other more profitable items once there. Also, in university towns supermarkets are prepared to take a loss in order to secure the long-term brand loyalty of students who are shopping at supermarkets for the first time and forming their opinions, and will go on to become professionals who can afford the more profitable products.

If you are smart you can take advantage of these to get food very cheaply indeed.

[1]: http://en.wikipedia.org/wiki/Loss_leader