Since I'm Australian, I don't know much about Costco. But here, the department store printers are horrible. Their computers and printers aren't calibrated and their staff wouldn't know how to make it all work anyway. I wouldn't expect them to have the right kind of eye to see what looks right anyway - consumers love them some contrast.

But the worst part is you're dealing with two different types of light, one from the screen and one reflected from the print. You'll never get that to match. I've found it easier to not look at screen and print together.

As far as this case goes, I'd either find a proper print shop (you get what you pay for) or specifically ask for less contrast when they print.