Please do not make such statements without proper research. A friend of my friend did exactly just that - replacing the leaking 3rd party ink cartridge with the original before sending in the printer to the service centre. The technician picked up a sample of the leaked ink and returned with a chromatograph, showing clearly that non-original ink was used, thus voiding the warranty. After my friend's friend admitted that he used 3rd-party inks, the technician said it is very difficult to develop leaks with original inks, so customers who try this trick are definitely out of luck.
Please refrain from encouraging such dishonest practices here. Vendors who sell such non-original inks are equally irresponsible if they promise that their inks will not damage the printers, or that the manufacturers will still warranty their machines. The verdict is out... the warranty will be void, and they will prove that you did use other inks.
And about your statements about printer companies not being able to make money by selling you printers at such prices... perhaps you're right. They should sell the printers for what it's worth (perhaps a $199 printer will cost $599), and let the 3rd-party vendors sell the ink. Afterall, the printer brands will probably be happier when customers trash their expensive printers with leaking inks by third-party brands. In the end, consumers like us will lose out even more, wouldn't we?