Study the ownership charts and it all becomes clear. There are not 10 companies producing 10 channels. There are like 3 to 5 companies producing everything you watch. So in your scaled down example, there's only perhaps two companies each producing 5 channels, and using the miracle of economy of scale they only each collect $10. You might very superficially think each channel costs $2 but because of economy of scale and intentional government regulation it costs like $9.50 to produce one channel, $9.75 to produce 2 to 4 channels, and $10 to produce 5 channels. The lights go out on the whole system if they don't get their $10 of revenue so they have to charge "around" $10 for one channel, you can forget $2 or even $5. Well, not everyones viewing patterns are going to match one corporation, so most people are going to end up needing to buy from both companies which is $20 so a la carte is dead. In an artisinal world of bespoke channels made by individual companies or people, a la carte would work, but economy of scale and financial pressures means everything you see comes from a very narrow funnel. And that narrow funnel is why its culturally changing from broadcasting to extreme narrowcasting and revenue is collapsing, but thats another issue.
Another analysis mistake is thinking channels are all equal and of equal value. Most channels are filler taking up bandwidth to keep competitors at bay. It is exactly like retail brick and mortar software sales in the 90s where you'd have a gigantic cardboard box containing a half sheet of paper and a CD in a sleeve rattling around in there. The fillers make little to no money but they make sure that a competitor doesn't have the space to set up something that could be a hit (its quite a downward spiral).
Eventually the cable companies are going to give up on trying to manage a system that delivers every channel to every station all the time, and then the game will really be on, and its a game of logistics and scaling and financialization that the cable co has already won, so best of luck to the new entrants, but other than provoking some short term innovation...