How have people not heard of adoptables… Am I just that deep in the furry fandom where it’s a daily, common, happily accepted concept?

Generally that’s an artist selling a design that they’ve/character drawn and not someone selling their character and then linking to imgur galleries of commissioned art.

Usually when commissioning an artist unless there is an agreement that the art is specifically work for hire and the rights are transferred, the artist retains copyright. I know for a fact that at least one of those artists you’ve commissioned gives you the high res file for personal enjoyment only.