I think you should wait until it drops to below $30 on Amazon or Newegg.
Buying used on eBay or anywhere else is a crapshoot. I learned my lesson when I purchased 2 used controllers for the price of 1 new one...never doing that again.
Make sure you get brand new ones. Amazon regularly sells them for $31.99 and that price rarely goes down, so any deal under $30 is good.
Sorry, I guess I should have been more clear. I just want to play games on my PC with a controller. I heard the 360 controller was the best one so that's what I was looking for in particular. I don't have a 360 myself. If there are any other controllers that are cheap and work well, then I'm open to those as well.