I saw the one at GC too, tempted just to try it out and see what it sounds like, worst case it's an easy return and I'd consider the $35 shipping to be the "rental fee" haha.
However, and maybe I'm wrong, but I was under the impression that these were something like $1800 or so brand spanking new. So a used one for $1899 just seems nutty to me. I can't find pricing on it anywhere though, so I guess you'd have to reach out to Kaos directly to find out what current pricing is.