I went thru the same dilemma today. Wife wanted double prints of about 170 pictures. That'd be about 340 total. Looked at shutter fly and they had a deal for $99 you would get 340 pictures, pretty close to the amount I needed. And on top of the 340 for $99, 30% off any purchase of $75+. so for $70 dollars I'd get 340 pictures, about 20 1//2 cents a piece. But shutterfly has some expensive shipping. When I seen the shipping rates, this was after I uploaded 120 MB of pictures, I decided to look elsewhere. Dotphoto had buy the bulk package 550 4x6 for $99(18 cents), I went ahead and did that deal, and shipping was only 5 or 6 dollars compared to 16 or so with shutterfly. Also DotPhoto has the matte finish that for some reason I like better.
KK