[dotnet00]

That only works when you're doing something like Starlink or Starship's development, where losing some prototypes is fine. However, that's not how JWST was designed, so losing many prototypes of it would be very costly. If JWST were designed with the consideration that it'd be mass produced, it would not be the JWST we know today and instead would be a completely different design (a rough comparison can be between OneWeb's more standard delicate satellite design and deployment procedure vs SpaceX's heavily optimized stack of less delicate satellites just drifted into orbit).

Most space companies are still doing their prototyping in the JWST style, so losing those prototypes is costly.

[looofooo]

Another JWST would have cost 1 Billion, so it is more than an Order of magnitude less.

[dotnet00]

That number isn't really convincing coming from the project that was initially expected to cost $1B and over time ballooned to $10B.