I picked the ship that gives me the extra talent choice and then spending all my money on getting more talents for the haggling skill, giving me 13 haggle.
It resulted in me not being able to buy anything at all. When trying to buy anything it says the max amount I can buy is a negative value.
Testing again with only 10 haggle and that brings the prices down to exactly 0 and the max amount I can buy is 1.#INF, but again I can't actually buy anything.
So I guess the highest functional value of haggle is 9