If the first stage is reusable, having a cargo launcher second stage that is none, reusable can be done for 30M.
First stage reuse is wall proven already.
> Starship will be unable to leave Earth's gravity well.
If its not reusable you can use it like any upper stage and it could launch anything anywhere you want.
> And if they can't refuel in orbit (which as of now, has only been performed a handful of times with small satellites)
The physics is well understood. We do it constantly with non cryogenics.
I really think this is overrated in how much of a technology risk this is. Specially if you have enough weight that you can invest in the solution.
Refueling is a schedule risk, maybe the first design will fail to account for something and it will take a couple iterations to get it right. There is zero risk that the problem is unsolvable.
In general I think refueling is a far smaller problem then the heat shield.
If they can't prove rapid reusability for both stages, it's extremely unlikely the cost will be anywhere close to as cheap as current estimates. And if they can't refuel in orbit (which as of now, has only been performed a handful of times with small satellites), Starship will be unable to leave Earth's gravity well.