I am really into scrapbooking. I order from Snapfish not necessarily because they are the cheapest but because they have the best quality in my opinion. I usually order a block of 250 prints for $20. If I don't use them up at one printing, the credit stays on my account.
About a year back I ordered 10 of the same prints from various places to compare quality. I did a variety of pics, underwater, outdoors, action, inside low light, etc and overall Snapfish seemed to have the best quality.