It's not just the overhead of showing up, it's the opportunity cost of not doing contiguous hours at a bigger job. It's very difficult to fill up a day with 45-minute jobs all over town, so he's basically working part-time if he takes a small job.
Where I live , there is a "call out fee". that prevents tradesmen from not being paid for time costs driving to job investigations .... The customer also pays for the needed diagnosis time too. So I do not see a reason why not do small jobs.
It takes time (plus money) to drive all over the place giving quotes for simple jobs that people end up getting multiple bids for and/or end up not hiring anyone in the end. Those costs aren't provided as charity, but rather has to be baked into the price of the jobs that do get accepted.
Charging a callout fee ( charge for tradesman to just come to job site) solves this problem. Any diagnosis time is also charged.
Hah, most places here charge a callout or quoting fee that they will refund when you order from them.
Overhead which probably includes warranty of the work and materials, and liability in case he damages something doing the work along with the additional regular costs.
Not to mention there's the possible, "I don't like you," fee.
Even easy job is probably going to take a few hours between scheduling overload, driving to and from the site, figuring out what needs to be done, and actually doing the work. Expensive? Possibly. But doesn’t seem out of bounds. How much would you charge to drive to an office to solve some problem even if it turned out to have an easy fix? I can’t imagine quoting much less than that.
Let's say he can do two such jobs per day and has 50% overhead. That puts his hourly rate at $700/4/2 = $88. That's good money, but it's probably less than what you make.