If this argument were true, dictatorships couldn't exist. However, they do.

Most dictatorships make no less than a half-hearted attempt to convince the population to support them.

And then they make a point out of terrorizing the people who don't support them. Just so the others have no trouble discerning whether believing them is a good idea or not.

> they either must be bought at an increasing steep price

You're assuming that citizen are united in what they want. That's usually not the case.