The whole "orbital slot" thing is absurd. Space is really big. Like, really big. And orbital mechanics being what it is, you could launch a satellite in the exact same orbit as a Starlink satellite but trailing a few miles behind and they'll never impact one another. If they are using totally different uplink and downlink frequencies they'll be effectively invisible to ground stations of competing services.

That being said, your napkin math is a bit off. A single Starlink satellite isn't all that valuable. It can only talk to ground stations in some region on Earth for a short period of time. It's the dozens of satellites per plane that make the service useful (24/7 coverage). While you can divide total revenue by the number of satellites, the service only works with a complete orbital plane.