I think OP means "what if the rocket fails". The answer is that building another telescope specimen would be quite expensive, even without any changes to the d

I think OP means "what if the rocket fails". The answer is that building another telescope specimen would be quite expensive, even without any changes to the design. The supply chains aren't set up for volume and integration and testing is very involved. I can't put a number on "the second telescope would be x% cheaper", but it would be very disappointing.