Honestly, even if you were to get him to agree to your pricing, I would probably stay away. He sounds like the sort of person who is used to bullying the people he works with to get what he wants, and in my experience, that almost always means a client who will be consistently unreasonable.

I've been on both sides of the fence, as a consultant (not in adult) and as a business owner who works with a lot of consultants and contractors. If either party is demanding or trying to push the other beyond what they are comfortable with, the transaction will almost always end up unpleasant or unsatisfactory for one or both parties.