Hewitt Packard (HP) heavily promotes their ink cartrdidge monthly subscription service when you buy one of their printers. Initially the monthly fee is relatively low - a few dollars. In my experience, supposedly based on my usage, they sent me one new set of cartridges over roughly the first year. But, my usage is fairly low, so I did not even need what they had sent me.
After about a year the subscription rate jumps to over $10 per month. I cancel the subscription. As soon as I cancel my subscription, they block my printer from using any cartridges they have sent me, even though I have not used them all yet. This happens without warning.
One day, you are merrily moving along with your work, you hit "print" and you get an error message that basically informs you that HP has stopped you from using the products you have already paid for. Interestingly they increase the monthly fee about 10 fold at just about the time I might actually be able to use one of the cartridges they have sent me.
This is an incredible, very aggravating SCAM from a supposedly reputable company! After 1/2 hour on the phone, they agree to extend my usage two more months - but these cartridges they have sent me should last about another year based on my prior experience. This is a SICKENING experience. AWFUL company.