Oligopoly _specifically_ describes what we have here. I learned a new word today.
From your link: "the exclusive possession or control of something", "a company or group that has such control".
You must be trolling.
I'm not. But I do find it interesting how some people here don't like certain definitions and claim they are wrong.
You're describing markets the ways journalists are joked[1] about describing guns. Except you're doubling down and saying "No, you're wrong. All assault rifles are AK-47s, everyone knows what I mean when I say an AK-47, you know, a gun that shoots bullets fast and stuff!"