printer ink, it costs them like 3 cents to make each cartridge and they sell it for so god damn much.
they also go out of their way to have chips in the cartridges and in the printers that make the printer not function if any ink is even running low, doesn't matter if you want to print something in black and white you had better fucking buy more cyan ink
gotta love seeing everyone else celebrating something about the date that we are already done with