I know they'll do installs, but I don't know about buying it and taking it home. I don't know pricing through the apple store, but I've always heard it's notoriously expensive. I do know it's a good value to buy ram at fry's or someplace and install it yourself, and apple has a diagram and directions on their website.
Install yourself...I went from 2G to 6G (max I could go on Macbook Pro I have). Bought from OWC, good price & fast. Sent directions as well.
HINT: MAKE SURE YOU HAVE CORRECT TOOLS to take off back of puter...DO NOT STRIP the SCREWS. Easy to do, so AGAIN, find a phillips screw driver that is SMALL, SUPER SMALL or you'll screw yourself big time.
I completely agree! Do a quick search for RAM through google and you will find a lot of wholesalers who sell it for dirt cheap. As for installing it yourself, I hear it isn't that difficult, but then again, I have never done it. Hope this helps.