Simply answer! Demand, scarcity and great promises. This is the mix that causes many people to pay horrendous prices for new projects.
This is true.
As for the scarcity, it is because of the supply limit of those coins. The lower the supply, the higher the price that it will have during their launch. But that doesn't mean that it will stay high forever if the development starts to be off and dry.
But if it's a continuous development, the price increase is inevitable.