That's difficult since I don't think anyone at SpaceX has talked about Starship launch costs and it's even more difficult because the comparison will be even worse for Ariane.
For Falcon 9, the costs and payloads aren't just claims. You can go to SpaceX today and buy a flight.
For Starship, it's an in-development rocket with a focus on novel technology as well as cost engineering. Orders of magnitude cheaper is a great goal but it's impossible to know if or when SpaceX can achieve it.
