I think you might be confused because I offered to sell him a bridge. It's an old saying used when you're talking to someone who is gullible or naive. "If you believe that, then I've got a bridge to sell you." A long time ago a con man actually sold the Brooklyn Bridge multiple times to people with more money than brains, like our dear friend Jon. "If you believe that, I've got an expansion to sell you."

/facepalm I've heard of that.. But that same saying is also used at, you guessed it. Trolls, so they can go live under it. My bad! :P