what do you tell them?

Anybody who knows computers knows there is gold in them. So unless you are asked about it don't offer the info.
What you are telling them now is fine and what I tell people. If they start asking more questions I tell them that everything is taken apart down to the screws and recycled. I also tells them that I have to ship different parts to different locations. When they hear that it usually ends the conversation since they realize that to get the $$$ it takes time and work and most people aren't interested in giving up their time and doing any extra work. Hard work is not for lazy people, and most people are lazy and want the quick buck.