So every year, I make it a challenge to myself to find the cheapest Holiday photo cards- and every year I end up at the same place... Sam's Club. You just cannot beat their prices. We got 150 for $34.50 which made them 23 cents each and if you pick them up at the store you don't have to pay for shipping. That's where all those other online places (Shutterfly, snapfish, etc.) get you- on shipping. Plus, the cards were ready in an hour- can't beat that.
I think Costco runs about the same but I am not sure as we don't have a membership there.