make (an amount of money) on (something)
To earn some varying, typically vague amount of money on some thing or transaction. The company stands to make an enormous amount of money on this merger. I didn't think I'd make any money on all these old toys, but people were actually willing to spend quite a lot for them.
make money on something
to make a certain amount of profit on something. I am sure I can make something on the deal. Can I make any money on this sale?