If it was so easy to diagnose then why didn’t you do it yourself?
What you are paying for is piece of mind and expert advice.
What would you do if someone wanted your expert advice on something you told them your fee and then solved their problem in 5 minutes and they balked at paying you?
This is the old saw about $1 for the work and $999 to know where to hit the machine with a hammer.
OK, following your logic, when is too much, too much? Remember that prices are not disclosed before treatment. Would a million dollar bill be reasonable?
If they knew the costs before being charged, you could make a stronger argument. As it is, they are not being charged for expertise, but for being ignorant of the costs.
What you are paying for is piece of mind and expert advice.
What would you do if someone wanted your expert advice on something you told them your fee and then solved their problem in 5 minutes and they balked at paying you?
This is the old saw about $1 for the work and $999 to know where to hit the machine with a hammer.