I discovered another cheat/bug.  I created stock of robots, put them up for sale and sold them.  Since my inventory was under severe constraints, due to demand outstripping my capacity for production, I didn't want the out of stock signs to loose me customer loyalty.  So I started deleting the Out of Stock signs.  I discovered that you actually got money for deleting the signs, even though the robot has already been sold.
HA! That's too rich!