>Even if a particular business has a lock down on a particular resource it can't control alternatives. The only way a monopoly can be sustained is that businesses price things so low that there isn't any profit in competing against them with alternatives.
This is empirically false, there are many ways a large business can lock down a market/resource, or very nearly so, and prevent competition from smaller upstarts. Look no further than two-billion-dollar-a-day-revenue Walmart, whose signature practice is running competitors out of town by undercutting them and sustaining the losses until they close.