They likely have to price it a bit above wired connections just to keep load manageable in dense areas, but it puts an upper bound on how badly monopolist incumbents can treat their customers.
While I don't think it will actually replace cable/fiber, I think it will drive prices down and service quality/customer treatment up, so its existence is a huge benefit even for people in populated areas that will never actually use it.
That puts an upper limit of 1.2 million worldwide simultaneous 100 Mbps streams, and that's probably being too generous. In a given region the limit is much smaller. The numbers I saw said 500k simultaneous 100 Mbps streams in the US.
Overselling can push those numbers up, but I don't think they can oversell enough to take them to a trillion dollar company.
You’re vastly underestimating how much you oversell as a consumer ISP. Fiber companies with dedicated lines to your house can’t even handle all of their customers pulling 100mbps at a time because the bottlenecks are the IXPs.
The AMS IXP is one of the largest exchanges in the world, and it only hits about 10,000 gbps max per day.
You’re also forgetting that $100/mo is a cost offered to consumers on the ground. Commercial shipping and military won’t bat an eye at paying $1000/mo for a measly 10mbps to a ship in the pacific. Oil rigs, mines, military bases, etc, etc.