> then aftermarket ink is fine
Then why don't they allow it, perhaps with warnings?
They don't block after market ink because of quality concerns, though they might claim so, they block it because they want to make more money from you themselves through ink sales. The common response here is “but they make a loss on selling the hardware!”, to which my response is “their bad pricing decision is not my problem”.
My roomba had warning in its guide that third party accessories may not properly work with the device. I was like pshaw you're just nickel and diming me!
But indeed, the third party brush caused the robot to have all types of errors. Some third party parts did work, just not the brushes. I guess there's some sort of strict size tolerance and the third party ones were a bit too big or small.
But I had only myself to blame for that.
I agree that "making loss on the hardware and using ink to offset that" is a very bad business decision. I have an 10+ year old HP Deskjet 4515 Ink Advantage which had a high initial price but cheap refills (black ink is pigment, but color cartridge is dye, but is UV resistant if printed on good photo paper), and that thing never created any problems for me hardware or software wise.
I can still use any print I got from it even after a decade. Ink's that stable on these.
From my perspective, 3rd party ink or toner is a support nightmare, esp. if it's bottom of the barrel. Again, from my perspective you should be able to take the responsibility and use these if you really want, but any ink or toner related damage might be out of warranty then (HP's genuine cartridges come with their own guarantees).
So, I can speculate that makers both offset the price and don't want to handle support tickets related to 3rd party ink damage for lower end devices, and buyers of higher end models are either using 1st party ink, or fine with paying the repair costs if their 3rd party installations go haywire.
Also, it's possible that kits for higher end inkjet systems (large format/plotter systems) tend to be higher quality since these models cater to professional shops which needs high quality supplies.
Lastly, I talked with someone who said that they buy the cheapest paper and cheapest ink because the printouts are disposable for them, and I find that point entirely fair, too.
My main point was underlining the fact that ink is not something simple in formulation. I don't defend banning 3rd party ink, but just pointing out some facts. I believe everybody can carry out their own fafo procedure.