Hands down I’d believe sam’s to be cheaper, quality wise??? It may be better to do them at home, I also like the ability to print pictures when I want them instantly, for me I accept the additional cost, (rough figure) for the option to print them when I want. I have had some pictures printed for me at labs, and I’d say my printer prints at very least as good as the best pictures I’ve had printed, and better than most cheap “store printers” (walgreens). Inital investment, cost of ink, cost of paper, I highly doubt would ever make it cheaper. I’m running an Canon i960 the printer got good reviews on printing quality and speed, I also like that I can print straight from my camera without a computer with the picbridge option, though it’s conveinent, the picture quality suffers when printing directly from the camera. I also like that my printer has 6 seperate ink cartridges, so you only have to replace what you need, I’m about 2 ink cartridges to 1 on photo magenta and black to all the rest. The downsides to my printer is it’s not a very good text printer, because it tends to use a lot of ink for text and it’s slow for text, even though its one of the fastest picture printers 
go figure.
If I want to print a bunch of pictures for people, I can just have someone else print them for cheaper. I have a co-worker who figures it cost around $.30 picture to print on his printer, though I don’t think mine is that high, I would expect it to be around the $.20 mark.
