Cheap printing

After extensive research, the cheapest place I've found for printing small editions of large scale color is Short Run Posters. If you are OK with their logo on the back, it's only $2 for an 18x24 color print, $4 without their logo. Only an extra $15 for rush production, it's amazingly inexpensive considering the next closest place I've found as far as cost is set somewhere around $4 a square foot, making it more expensive than the DFAS. Their "sister site" Xeikonprints.com is also pretty nice... more expensive, but they have a whole lot more options, as well as a 24 hour printing service (for 50% more).

Just keep in mind the more you get of a single edition, the cheaper each print will be. That's true with every printing place.