I have a couple of HP4100-series "workgroup" laser printers. In my business, I print a good bit (over 500 sheets a week), and one of these high-capacity cartridges lasts me over a year. Before I picked up these printers, I was using an inkjet where each $22 cartridge lasted about a week. Do the math: the savings are massive, more than enough to pay for the (used) printers!
I've been buying my toner cartridges from Monoprice since they started offering them, and I've never had a problem with them. The same factory cartridge is $120+. Sure, this one is "re-manufactured", but since the drum is new, it might as well be brand new.
PROS: Inexpensive! High-quality re-manufactured cartridge (new drum). High-capacity cartridge, rather than standard-capacity.