Your operational and marketing and capital costs apply to all ISP's, not just Starlink. The net present value of $6.25 monthly at a 3% interest rate for 20 years is $1100. For 50 years it's $2000. So that's your breakeven point. You might be able to wire up an entire town for less than $2K per customer but you certainly can't do rural customers for that.

Shotwell has said that Starlink will be competitive with $80/month internet.