I have long ago learned that if you do good work and are a likeable person, the clients will pay ANYTHING you ask.
Peter Grey Piano Doctor
This is true to the extent that you are good enough that enough (well to do) clients want you to work on their piano but also your competition around you?
FWIW, the technician that worked on my piano recently and who travelled to mine included 30 miles travel (round trip from his base) into anything he quoted for. After that he added on 45p a mile to cover travel which I was more than happy to cover bearing in mind it was approx 100 miles and an hour an half travel each way. Another well known technician that I was considering and spoke to quoted me a similar cost for the work at my place but his travel fees included return train tickets to me, cab fare from station to mine as well as 3 hours travelling time billed at his hourly rate. That worked out to be significantly (4x) more for travel than who did the work for me. Both were top technicians known to work on Steinways and Yamahas prepped for concerts in the UK and Europe so at the end of the day, travel cost was the determining factor. It might be worth getting some friends to call up your competitors and asking them what they charge for travel