Kyousouka
Vicemage: I've never been able to find pre-printed sheets in bulk. Could be my requirements though - I need ISO paper sizes.
Paying 50 cents per sheet sucks, but such is the price of convenience.
Wish I could remember the shop I got it from, but I've got a pack of 100 Canson Fanboy (God I hate that name) Manga Art Boards that I picked up for, I think, $25-35 USD or so. They're the 10 x 14.25, 150 lb bristol ones, with the preprinted lines. They do also do the Comic Art Board size, at 11 x 17 (I've got a pile of them already, though, from classes back in college, and thought I'd try a smaller size). The shop had both of them, for roughly the same price.
I don't use them very often, though, because I do a lot of my pencilling at work and can't carry a larger art board with me as well, and because I honestly hate reassembling scans.