It doesn't really matter how inefficient you are if you have the cash to buyout any potential competitors before they have a chance to threaten your bottom line.

In a purely capitalist society wealth (power) accumulates at the top. Money creates money so whomever starts out with the most money tends to win. This is why highly capitalist societies turn into Dubai, with an ultra rich ruling class and a serf/slave class with little in between.

Seriously, has no one on here heard of the Gilded Age? Of anticompetitive practices by Standard Oil before regulation was brought in?

Are you talking about the outlawing of railroad rate rebates or the break up of the company?

Just as an FYI (and apologies if you are already aware of this), but Standard Oil had already lost about ~25% of it's market share by the time it was broken up. Rockefeller had no influence in Texas and California where the wildcatters had moved to and found oil.

But then everyone would create competitors so you would buy them out, and eventually you would run out of money.

You essentially said the same thing that the comment above you, just in a less succinct way.

A regulation-free system is not a stable equilibrium, so the conclusion will not be regulation-free.

Of course it's the logical conclusion. Power abhors a vacuum. Do you honestly think that companies are going to sit back and not try to take that power for themselves?