No chance it's going to be more expensive than comparable wired - fiber or cable - Internet.
You're leaving out the vast cost to build & maintain the wired infrastructure. Tax payers & consumers in those developing nations have to pay for that. That cost has to be included with the monthly fees to do a serious comparison.
The cost of building wired infrastructure has an inverse relationship with population density. This might be more expensive than wired internet in dense cities. The metal of city buildings and the high density of transmitters might make the performance lower in cities than suburban/rural areas.
The Manhattan and Tokyo speed tests are more important to me personally than The Grand Canyon and Indian Ocean speed test.
A key strength of the proposed network is its ubiquity, which makes it most competitive in un(der)served markets than in high-density cities. They can't just hover more satellites over Tokyo, so the service would inevitably become fully loaded there.
You're leaving out the vast cost to build & maintain the wired infrastructure. Tax payers & consumers in those developing nations have to pay for that. That cost has to be included with the monthly fees to do a serious comparison.