Indeed they do and what is reasonable for one may not be reasonable for others. However from the limited detail given by the OP, I am relatively confident I could verify the integrity of this underground garage supply cable without the need for any prior site visit, or any time collecting materials, or any time writing quotes/estimates for the work. And I doubt I would be on site much longer than 30mins to just test the cable. I appreciate some customers involve long durations of travel time, however there are also just as many that are local calls, or visits that can be made whilst passing to or from other jobs. It would not be an urgent out of hours call-out, just a drop-in visit at the next most mutually convenient time.
Very frequently on the forum we get members telling DIY posters who are trying to fix an electrical problem, they should not touch it themselves and they should call in professionals. Most of the time they are trying it themselves as they think that electricians charge too much. Unless the OP is in the middle of nowhere, or in the middle of a major city with travel and parking restrictions then I would guess there are at least one or two relatively local competent electricians who are able to visit. Not sure how much you would be charging to just test the cable, (not fix any problem found), as a call-in whist passing to from other jobs? But from what you post suggests, it may be one of the reasons DIY'ers do keep trying it themselves and don't call in professional help. Possibly you should avoid reinforcing the expectation to customers at all electricians visits will be prohibitively expensive.
Doc H.