I rarely buy anything off eBay anymore (and never have purchased bikes/parts there).
When I do buy something I always use a sniper program and walk away. eBay just has too much world-wide exposure to millions of idiots who have no idea what something is worth, only that they want it, and now! And if you want it too, that makes them just want it more.
A year or so ago I saw a new Martin guitar strap and strap button, current production that you can buy in any decent guitar shop for about $35 that ended up going for $300 - and there were three idiots with lots of feedback (i.e. not newbies or shills) bidding on it!
John