Grab a used HP LJ 4+ (or a 5 - But NOT the 5L or any of the consumer level 5's, make sure you get a workgroup level printer). My roommate & I got one for $50, with a 10/100 jetdirect & 22 mb of RAM. Even came with a toner cartridge.
12 ppm, 600 dpi, and absolutely bulletproof reliability. I regularly see 4+'s with over 500K pages, & I've seen a few with over 1 million pages.
The maximum capacity cartridge is good for 8,800 pages & is $93.99. That's $0.0106 per page @ 5% coverage. You will not get a cost that low, or equivalent office document quality with ANY inkjet.
HP toner cartridges are warrantied as long as they have toner in them - If it dies, they'll replace it. No questions asked, no need to return the old cartridge.
Viper GTS