... You might want to get a few estimates from a few plumbers.
Having one estimate isn't enough to get by, IMO. By the time you talk to the 3rd plumber, you're more knowledgeable about the problem(s) AND the potential solution(s). Call a 4th one if you like. And ask each of them about what 'the other plumber' says. For example, if the first plumber wants to put in a new washer, fine. If the 2nd plumber says he wants to install an air chamber, ask him why he can't try the washer replacement first. And go back and ask the 1st plumber why he won't recommend an air chamber. (I'm not advocating either solution, in and of them themselves, nor one over the other. I'm just using them as an example of how you learn by talking to more people, and how you end up asking MORE questions based on the MORE you learn. See what I mean?!)
My best to ya and hope this helps (keep the cost of the 'fix' to a minimum.)