And soon enough your son will also. While undergrad work is, at times, boring and unfruitful, I would think that one question will help him see the light.
Ask him if he is making a 30% return on his money. It’s a simple question and the one that most successful business owners know by heart. If you’re not making 30%, then you are not in a successful business venture.
I was once part of Nexgen. They went out of business because, from what I hear, their sole monetary income was from new recruits. Ask him how he makes money. And tell him that a true business venture makes money immediately. Otherwise your expenses far exceed your profit, and you lose in the end.
Don’t, however, stifle his entrepreneurship. It is a gift. Just let him know that he needs to focus his energies on profit. If he spends 600 bucks, he might as well buy a jet ski (or something else) that he can sell for 900 bucks within the week. That’s a business.
Let him mature to a true businessman. It could reap rewards in the long run. For now, show him how much he has lost, and then show him a better way.