You are going to pay whatever the prevailing rate the vets can get away with in your area and how far they have to travel to your horse (the farm call fee).
The last hoof x-rays I paid for were in 2019 and were $77/each, plus the road fee. I could drive an hour north or northwest and pay 2-1/2 times that amount.
The vet is a mobile lameness specialist. He left an equine facility further north that charges a lot more money but working in that world was not what he wanted to do.
While he was here, he also popped the gosh awful plaque caps off this same horse's lower canines and didn't charge for it -- probably because this particular horse is so good, he did not need tranq'd to have his teeth fixed.
It isn't just the quality of the pictures taken but the skill of the eyes reading those results.
I've paid anywhere from $45 - $125 per depending upon where it was on the body and who and where the location of said picture taking took place.
Going rate and what the local horse-people will pay can often determine pricing.
Don't forget the farm call fee many charge too....
Your vet should be able to tell you their fee charges for such pictures and they know how many is customary done for diagnosis, then if special needs done how much each additional would cost.