I'd have a very hard time turning down anything over $10m at any age. Even if I thought my product might be worth billions.
That's nice but not "set you for life" nice.
In my mind I would still risk it at $1m because $40k isn't enough for me to live the kind of lifestyle I would want to live and ensure I could do it until I die.
Six Flags ordered 100 machines putting him at 550,000 revenue for a single customer. As more momentum picks up and they pull in more customers, he'll be well over 30m revenue in a few years time. Smart move from this kid. Bill Gates didn't get his wealth by selling out at the first offer, regardless of his age.
This is the crux of what is being discussed, as with the risks involved in that.
I think taking the money and using it to fund another business in a few years is the best course of action.