I have an HP inkjet printer that qualifies for their Instant Ink program. I am currently on the free plan that allows printing up to 15 pages a month for free. When the ink runs low they send me more ink (for free). If I happen to go over 15 pages/month, its only like $1 for another 10 pages, so not a big penalty.
That sucks to hear. In my case I am not paying them a dime and still getting free prints out of it.