Everyone already knows buying off-brand ink refill cartridges saves money, but you're still paying more than oil, blood or petrol. Cool Tools suggests one possible solution: buy ink in bulk, and hook it up to a continuously refilled system.
Photo by Denis Gomes Franco for Wikipedia.
These continuous ink systems hold a large quantity of ink, and modifies the way it feeds into your printer, which has a side effect of voiding your warranty. You can gather the parts and modify your printer yourself, but Cool Tools recommends Cobra Ink, a company that does the modification for you for $US50-$US100 over printer's RRP. The upside to doing it this way is that Cobra Ink supplies their own warranty, since Epson or HP's is voided by your mod.
If you do a lot of colour printing, this seems like a good moneysaver. If you're like me and only print black and white, with a little bit of colour occasionally, a laser printer might be better, since that doesn't have the drying out problem.