HP wants you to mail them back for free, but I recently saw that a charity collecting them. Do they make money?
The charities that collect empties get a buck or two per cartridge by sending them to companies that refill or remanufacture the cartridges and sell them. Some are even operating divisions of cartridge refillers:
Forgot to say that there’s so much profit to be had by the refilling folks that they pay the shipping to get the cartridges from the charities.
Whether you send them back to HP or to a local charity, they get rebuilt. You might as well give them to the charity so they can benefit.
I always assumed that HP destroyed and recycled the toner cartridges sent to it, so that there were fewer available for refilling.