Nice
I did a thing like that (but less serious and advanced) a month or two ago:
Telemarketer: "Hi, my name is xx from yy. Am I talking to Mr. Z?"
Me: "Do you want to buy a washing machine?"
Telemarketer: "Excuse me?"
Me: "A washing machine. Do you want to buy one?"
Telemarketer: "Erm.. what kind of washing machine is that..then?"
Me: "Actually I'm not too sure what exactly it is.. I think it's an Electrolux, though"
Telemarketer (with a superior voice): "Heh..You've got to know what you are selling, don't you?"
Me: "It's a washing machine.. it.. uh.. washes clothes?"
Telemarketer: "ah.. well.. how much is it then?"
Me: "eight-thousand and fivehundred dollars (*)"
Telemarketer: "That sounds a bit too much for me."
Me: "Ah.. I'll have to ask someone else then.. but thanks for calling!"
Telemarketer: "Okay, bye."
Me: "Bye."
(*) : This is is sweden, so I had to change our currency to something similiar in dollars.
Next time I will ask the person to hold for a bit, and continue with what I was doing (watching TV, reading, computering) and see how long the person will hold.
Bonus points if the person on the other end can't hang up and break the call immediately if I don't hang up as well. He/she will lose precious time bugging other people.