Why are top quarks heavier than bottom quarks?

[TCS]

Up quarks are half the mass of bottom quarks, while Charm quarks are ten times heavier than strange quarks, and top quarks are 40 times heavier than bottom.

Why do the relative masses of the particles change? I had always that that they were just higher energy versions of the same particles or the same particles in different states.

 

[tom.stoer]

Afaik there is no theory which can explain the quark masses and which can tell you why there are three generations.

The heavy quarks are not just higher energy versions in the sense of excited states. They have different flavour which is a quantum number like (strong) isospin.