Alternatively, no one enters the market because the monopoly company can still undercut them. Another bigger problem is that the monopolist pushes the low cost

Alternatively, no one enters the market because the monopoly company can still undercut them. Another bigger problem is that the monopolist pushes the low cost of delivered goods or services on third parties (see the gig economy). That race to the bottom harms people, but there will always be takers for those jobs in any society without a good social security system.