Because that's what will make this whole thing fall apart. A motorized phased array antenna isn't going to be cheap to recoup.

Surely less than $100 a month, which is how high some existing internet can be anyway

you already know why.

https://news.ycombinator.com/item?id=22940781

Shotwell has said that it will be competitive with existing Internet pricing at $80. She didn't say it would be $80, but competitive with that pricing. Read that as you will. I'm sure that's only the starting price, that you'll be able to pay a lot more for more bandwidth.

$100-150/mo for satellite based service would be totally reasonable (depending on data caps, etc). When you figure the average home (wired) internet connection is in the $80/mo range, cell phones start around there too.

The people who need this service are the ones whom are so far out that they have no option for DSL, Cable or even 4G tethering.

I wonder if it will have location-modulated pricing; $80 wouldn't be competitive where I am.

If anything, I can imagine them ramping up prices in higher-density areas (where other more competitive broadband providers are available) to avoid oversubscription.