We also need to factor in the cost of replacing all the satellites every 5 years or so, as they only last this long in the super low orbit that they will be in.

We also need to factor in the cost of replacing all the satellites every 5 years or so, as they only last this long in the super low orbit that they will be in. So it's ~10 billion every 5 years, not just once up front. So 10.000.000.000 / 5 / 12 = 166.666.666 bucks per month Say an average subscriber pays 20 bucks. 166.669.666 / 20 = 8.333.333 You'd need about eight million subscribers paying an average of 20 bucks a month to keep the business sustainable.