How can an individual get rich? There are only two ways:
One way is to steal his way to riches. He can use the “political means”, which is to use violence or threats of violence. People are coerced into giving up their money.
The other way is to persuade people to voluntarily give up their money. This is the “economic means”. This requires the individual to produce something that other people want.
Libertarians reject the initiation of violence or threats of violence, so they reject the “political means”. So in a libertarian society, if somebody is very rich, it must be because he has produced things of great value to other people. There simply is no other way for an individual to become rich.
The “desire to become rich,” usually presented as a bad thing, can be interpreted, in a libertarian society, as the “desire to satisfy the most urgent and important needs and wants of as many people as possible”.
In other words, greed is good, for want of a better phrase, as long as the economic means is used and not the political means.