You can get some real good deals on eBay, but you have to know what you're doing (as in, knowlegeable about the price), and be lucky. I've gotten some super deals as well, a lot of them were luck in that nobody else put in a bid.
I generally go for the custom stuff, or buildings. Stuff you won't find in the hobby shops. On some buildings, you know you got a good deal when the nice building price is less than the shipping cost (and I'm talking about valid shipping cost, not the inflateds).
Kennedy