It's not quite that bad (yet...) - it has reasonably clearly labelled subscription and non-subscription cartridges. So when you cancel the subscription, you just throw the non-subscription cartridge back in.
If you're printing quite a lot, but not enough to justify a laser printer, then they can work out okay. The vast majority of people would indeed be wasting money though.
I had to pay for a static IP just this week because it turns out the new ISP uses CG-NAT.