The starship is built out in the open, the whole world can watch. Because of that, there are pretty good estimates for how much construction costs. If you take the more pessimistic estimates, my statement would still hold true.

Also, as a reminder, even without knowing exact numbers you can still make some ballpark assertions with confidence. For example, Jupiter has the mass of more than a dozens earths. I could look up the actual number, but I can be pretty damn sure it’s more than twelve.