Teaching Escrapping. What to charge?

I was wondering about this predicament a while ago & came up with this answer.

Get them to give you 125 computer towers etc inc.
You break the escrap down & show them how to do it, as you break it down, and they help.
You sell the escrap, show them the receipt & keep the money.



At the time I was thinking about the gold factor, teaching that as well.
$2000 may seem a lot of $ to ask, but gold was $300 once & at the time they could have learnt it for $300...