That's a common myth. The wealthiest you speak of are actually anti-libertarian, free market economics. They frequently use cronyism as a means to increase their power and wealth. Those tippy-top earners are where they're at because of government, not because of the free market. I won't speak for all of them, but I don't think you'll find many libertarians that believe in gov't picking winners or cronyism, to consolidate power and wealth.
Ultimately, if ya boil it down, libertarian economic beliefs are about voluntarism, not statism, so any influence by the state is not "the market".
There's not a finite amount of wealth. There is no "pie" that is only that size and can't be added to. Wealth can and is created and in a market economy, both benefit because "the rich" make the goods the rest want and the rest are willing to pay for said goods.