Very rarely do I walk away from a job.
when I do it is usually because the customer is a jackass.
I just price it out. if the customer really wants it fixed then they will pay whatever you ask.
many times i have tripled the labor and they jump at the price cause they want the problem resolved.
if they walk away its due to cost of the repair not your unwillingness to complete the repair.
do a lot of 1500 dollar compressor jobs on the high line units... hate doing it but love the money.