I wonder about the economics, though. Intuitively it doesn't seem like it can be more efficient to launch constellations of satellites than run kilometers of cables, even if you have to run 20 km for each customer. That's, what, $10k a pop? So around two orders of magnitude cheaper than a satellite? Something isn't adding up for me.

Starling is 10k satellites shared across the entire planet.

A satellite will serve thousands of customers, whereas a fixed line only serves one. I think 10k is also severely understating the cost per customer. There's like hundreds of metres between these houses at a minimum, and in some areas possibly Kilometers from house to house.

Intuitively, what's the cost to get to orbit? SpaceX's Falcon reusable rocket lowered the cost to get to space by an order of magnitude or so, so you have to factor that in.