I would actually think that the 9% they cut off would be more likely than the 91% to be using Reddit.
And anyone would complain even more if they're paying much more and getting less.
Worth noting, however, that there are also rules on using one's user page as a promotional piece. It's much more loose obviously than the criteria for what goes in an article, but you absolutely will get smacked if you use your user page exclusively for advertising.
That said, if you pay more up-front for something like a Brother laser printer, it should last you a lot longer and be on the order of 10x cheaper per page. People see Instant Ink as "cheap" because they've probably never tried the much cheaper alternative, and they see it as "convenient" because they've never had a printer that lasts several thousand prints without a cartridge change. It's really sad seeing so many people who can afford the upfront cost of a laser printer falling for this scam so often.