Not to mention that the private companies will work to avoid said competition. Little wonder why ISPs refer to creating networks where one already exists as “overbuilding”
When I look around, there are multiple businesses usually near each other that compete. Home Depot and Lowes, Walmart and Target, Burger King and McDonald’s. ATT/Verizon/Tmobile.
But it is possible that if you pay to build out an entirely new network to a place where Comcast has a monopoly, and the customers would rather pay Comcast $5 less than whatever the lowest price you can charge is, then you would see negative returns by paying to build that network (since the cost of building out a network like that is so astronomical, and Comcast obviously does not have to pay it so their COGS is much lower).
But it is possible that if you pay to build out an entirely new network to a place where Comcast has a monopoly, and the customers would rather pay Comcast $5 less than whatever the lowest price you can charge is, then you would see negative returns by paying to build that network (since the cost of building out a network like that is so astronomical, and Comcast obviously does not have to pay it so their COGS is much lower).