It probably varies according to the specific model of each brand: our old HP all-in-one (model# now forgotten -- maybe 7130?) had separate print heads -- and wouldn't print in black unless it had a full set of "active" color cartridges as well (which "expired" whether they were used or not: the printer kept track of the date and of the date a cartridge was installed and of its predetermined "expiry date"); the Epson WF-4630 and XP-4100 all-in-ones both have separate print heads, but how difficult they are to clean or replace I have no idea.
Each of the printer manufacturers produces printers with varying characteristics. My Epson RT-3750 has printed over 50 multi-page multi-color documents this weekend. Its ink bottles contain ink and has a special cap which fits into the tip of the ink tank on the printer to open the gate and allow filling. The ink bottles contain so nozzle, no electronics, just a plastic bottle with ink. And yes you pay more for that printer but the prices HP was charging for a set of ink cartridges would have far exceeded the Epson's initial cost which included the ink bottles of which I have 5 still unopened. So it is a pay me now for longer term low cost or get $30 a cartridge'd to death.
There is 'scam' in the thread title, but I thought it was for scams about inkjets. Or is that what the kids are calling it now?