If each Super Heavy Starship costs $300 million and has $1 million in operating and maintenance cost per flight then the per flight cost is $4 million. Super Heavy Starship is supposed to launch about 100 tons to orbit.
Assuming that 800 Starlink satellites are launched by April 2020, then SpaceX will start doubling its revenue from $2-3 billion to $5-6 billion in 2020 and ten billion in 2021. This will mean that SpaceX will be able to afford to build dozens of Super Heavy Starships.
It will be trivial to create a lunar mining operation with a 100-ton fully reusable SpaceX super heavy starship. This will further reduce fuel costs by 5 to 10 times for orbits beyond low earth orbit.