What would another James Webb Telescope would have cost? Far far less then the first. Sure it is costly to destroy a prototype, but not as much as you think.
Most space companies are still doing their prototyping in the JWST style, so losing those prototypes is costly.
It was a huge publicity boost for NASA, but not actually an efficient use of resources in terms of % shuttle missions * total cost of the shuttle program. That’s arguably unfair because of the sunk cost issue and how the budget was setup, but manned missions are inherently expensive and even more so if you’re trying to match arbitrary orbits.
Also no reason why it can't be an ISS, and no reason you couldn't link multiple together.
Pretty useful to have a reusable grain silo you can launch and land.