This depends entirely on how much spectrum, how much power, and how geographically diverse you want to deploy. Without going into too many details, I can say

This depends entirely on how much spectrum, how much power, and how geographically diverse you want to deploy. Without going into too many details, I can say that purchasing 500 milliwatts of EIRP transmit power in a small urban area (<10 sq km) of 5 MHz of spectrum in one country of population < 10mm people can be had for ~ $2mm/year.