This. Pyramid schemes are necessarily unsustainable, because everyone who gets involved is solely relying on a windfall for getting still more people involved, and while the world is overbreeding, it's not at the rate they need. As soon as you find end users who will see some kind of net value even after growth stops, you have something that can sustain itself indefinitely. At worst it could be a bubble of investment in training capacity, if they overshot the market size.