they normally sell for between $50 and $130, well, at least thats what I see them go for.
That estimate may be a little low. I sold my crappy Barney converter and the bidding went over $70 (and that was 2 1/2 years ago when TZD still stocked Mirai adapters!) Granted, I had a nice picture and good feedback, but Barney converters are the worst of the bunch and I even described how it often took five minutes of screwing around to get the thing to work.
After the Miria adapters sold out ($99), TZD sold the "secret stash" of their remaining 5-7 Kisados last summer ($150 IIRC) and I've barely seen them anywhere since. The handful of ones that have turned up are usually part of a larger lot, so prices are hard to judge. A lot of sellers also mislabel their Springboard and Miria adapters; assuming anything that isn't a Barney converter is a "Kisado." These days, I'd say that a well-listed Kisado could fetch $200+ if a seller let the auction run for 7 or 10 days. I saw one go for $250.