Most minor professions from house builder to car salesman have a little bit of institutionalized dishonesty built in to them. This has creeped in by increments

Most minor professions from house builder to car salesman have a little bit of institutionalized dishonesty built in to them. This has creeped in by increments over a long time and so doesn't strike the practitioners of these professions as dishonest at all because "that's the way it's always been done." People with a fresh perspective will compare it with other, less "storied" professions and it will feel (perhaps rightly so) like a scam. Do some research and negotiate up front. If you make an unexpected demand at the end thats quite different than the usual, you'll make the photographer feel as if they are the one who's being scammed. If they know up front that this shoot is going to be different than "the norm", they will often be surprisingly willing to think differently.