I was wondering why the the price of this specific auction of MT500's is so high? I've seen others that went for around 20 bucks. Is it the fact that they're in great shape and actually work?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=296&item=5768893934&rd=1

It only started at $50, and given that they work (and appear to be in good condition for 20 year old radios) does go a long way to explaining how the bidding has gotten up to $100.

Bear in mind that it's Ebay, and sometimes auctions won't fit the average - it all comes down to how many people really want the same item.