I always hear the argument from left-leaning people that the free market has no restrictions thus creates monopolies or oligopolies.
Take this scenario:
Person X is very wealthy and can afford making better investments and provide more options in his/her company.
Person Y and Z: Each have their small business, and cannot afford increasing their options in order to compete with X.
Thus Company X becomes a monopoly making companies X & Y break even, and making no other business join.
I learned in Economics class that a monopoly or oligopoly does not allow new firms to enter the market.
I know that government regulations make products, job creation, investments , productivity more expensive.

But what is the Libertarian response to this argument?