The James Webb Satellite seems to be a highly successful project and it looks like humanity will get useful observations from it for many decades to come. But the question is... why not make 3 more copies of JWST and launch them into orbit so that we could get new data 4x faster? Or even 9 copies to get data 10x faster?
Since all the engineering has already been done and the satellite has been tested in practice, surely this would be much cheaper and faster than designing a new satellite from scratch? And you'll get a bit of savings from economies of scale, as you'll make several copies of the same part.