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.