It's not possible to give you an accurate answer with the information provided. There are many factors that go into a price.
- How much drywall?
- Additional demo
- Replaceing trim and millwork
- additional time to aquire materials
- removal and replacement of fixtures on said wall
- additional protection of adjacent surfaces
Some or all of these things may apply to your specific situation.
If you question the cost, the best thing to do is discuss it with the contractor. It's best to discuss the details now rather than latter.