Absolutely! In a lot of cases it's darn near cheaper to buy an entirely new printer than the ink cartridges. I see basic, name brand printers at my local Rite Aid for $30 all the time. It's ludicrous.
Back when I did have an inkjet printer I used to refill the black cartridge myself, too. It could be messy, but was certainly cheaper, and in most cases it worked very well.