He's coldly rational:

The investors gave him $5 million. Large commitment, large risk.

Each customer gives him 15k per unit. Even a rare large customer who buys 100 ovens gives him 150k. Small commitment, small risk.

If he breaks his promise to the investors, he can't raise more money easily. It will be very hard to find another $5 million.

If he breaks his promise to the customers with a garbage product, he can more easily find a replacement customer for the much smaller risk.