I understand how the subscription model works. My point is that I think it is a very reasonable expectation that once you have an ink cartridge, you should be able to use it until empty. This was evidently not made clear to the OP. I'm saying that this seems to be a failure on the part of HP to clearly communicate the restrictions in place with the subscription model.
I'm not suggesting they violated their agreement with the user, I'm saying that the terms of the agreement could have been more clearly communicated.
You don't need to use the subscription model to use a printer, you can use regular cartridges.