I would expect them to price Starship at or below Falcon 9 from very early on. That lets them move payloads from Falcon 9 to Starship. Every Starship launch is an opportunity to practice landing of the first and second stages. It makes sense to include commercial payloads for their practice launches even if they do so at a loss, because they need to launch anyway and some revenue is better than none.

They'll charge what the market will bear, and it won't bear more than Falcon 9 (for payloads Falcon 9 can carry) because Starship doesn't have the track record of success.