When we use “Windows” we don’t complain that they’re not real windows. When we use a Mac, we don’t complain that it’s not real Macintosh apples. It’s just a name.
As the parent commenter says, you pay explicitly for a quota of printed pages, not ink or anything else. Therefore, they do define a price per page, anywhere from 10c on their cheapest plan down to 3.57c on their most expensive.
Is it a shitty practice? Certainly. But you explicitly dont pay for ink, regardless of the name of the product.