He is single handedly creating the product that is to be the source of their income from scratch. $65k is much less than half salary for this position.
But he's also been given a % equity stake as well. You can argue it's not enough, but he's got a % stake in this which is far beyond what most people have where they're working.
But that's not how it works. There are a lot of people who could do it. In fact, there are consultancies who could do it, probably better, for less than $65k.
