I’d be suspicious of most Adobe software for sale on EBay, you could be in for a nasty shock when you try to do an update.
I believe that Adobe are offering a 50% discount at the moment to anybody with a copy of Elements, if that’s any use to you. I availed of this about 6 month ago and got a full version of CS3 for just over €400. See the thread here, which Mr. H bumped recently