Small correction, no one will be able to pay for time on JWST. But if you put in a proposal for time and it's accepted, they will pay you. That's to make sure there is sufficient funds available to properly make use of the data you proposed for.
Actually that's sort of a large correction, thanks for pointing that out. Isn't it a bit of an inversion of the norm in astrophysics? I'd thought many grants included money for telescope time.