What are the possible costs of fullmouth dental x-rays?

Depends on location. The cost of a full mouth set of dental x-rays will depend on the area of the country you are in. Usually more expensive east and west coast. In midwest around $120-$150.
Varies. The price of anything, especially health procedures, can vary from doctor to doctor and city to city, and region to region.
Depends on need. A full mouth series will vary from provider to provider and even city to city. Commonly i belive you could count on a true full mouth series to cost $100-$200 depending on what is including such as a panoramic radiograph which will push it into the higher amounts.