> and becomes cheaper than any current terrestrial energy source at around $50/kg

Heck for $50/kg I could see it, too. Now with Falcon 9 or Heavy it's on the order of thousands, isn't it? Just need a measly two orders of magnitude improvement and then we can start talking.

Does gauging this based on Falcon 9 launch costs make sense now? SpaceX has already deployed two payloads of satellites using Starship. Falcon 9 is a deprecated system because SpaceX intends to use Starship for future payload missions.

We can't yet know the ultimate cost of Starship payloads. All we have is SpaceX projections of $10-100/kg. Maybe that is realized, maybe not. Given the scale of the LA launch site they're building, they intend to have the launch cadence to deliver lower launch costs than anything achieved with Falcon 9 or any other launch system ever created.