My spitball solution is to add an excise tax on revenue based on market concentration, potentially paid back to consumers or new market entrants. So if you own

My spitball solution is to add an excise tax on revenue based on market concentration, potentially paid back to consumers or new market entrants. So if you own 50% of a market, maybe you pay a 25% excise tax, and thus the market finds an equilibrium except in cases where a monopoly is warranted, despite the high tax.