If they are actually doing some work (editing significantly after generation) then they are protected on two fronts (currently, active cases may change this):

* as discussed elsewhere in these threads, the judgements pertaining to copyright not applying to generated work all only seem to cover entirely generated work where there is very little human activity after the prompt.

* even if the generated work is public domain, the derived work (the edited version) is not necessarily so (much like Disney's derived works created from the tales of Hans Christian Andersen's writings).

If they are not doing significant work after the ghostwriting, then sod'em, they are earning the stigma of essentially committing fraud to get that profit from the work.