The ONLY place where it is mentioned that it is only the caps, no the entire keyboard is in the name of the auction. The description just goes on and on about the keyboard, the switches etc. It seems as if they want to trick people to buying it believing it is a complete keyboard.
Looks like a scammer to me.
Edit: Ok, a bit harsh. He will probably send you the caps, and they aren't that expensive, but I still consider it shady behavior to try and mislead innocent customers like that.