In fairness to those other trades, there are costs incurred there, too.
A hairdresser, for example, has far more than $200 sunk into his/her tools, and depending on the work venue, either is a business owner, or pays a fee for having a spot in somebody else's salon.
A good computer technician has hundreds and hundreds of dollars in tools, some of it software and some of it hardware. I worked as a computer tech, and it was impossible to do without having a series of various computer 'husks' to do work and testing on. I used 3 computers. At the time, they were about $1,000 each. Usually they can be pieced together from parts that somehow 'accumulate', but those parts had to come from somewhere, so while they seem 'free', there's a red mark in a ledger book for them somewhere.
However, I only say that to defend the other trades-- having been a computer technician and now trying to be an amateur guitar-maker, I can say that the skill set is different, the tools ARE less expensive as a tech for sure ($3,000 might only buy you a HALF of a needed piece of machinery!!!), and the sheer volume of computer techs compared to professional luthiers is quite different. <grin>
Back to a point, though-- it does depend on what's being delivered. A person could easily do the electronics for a guitar with nothing but a soldering bay, a meter, some solder, and some wire. (any needed parts being at the cost of the client).
I'm pretty good at setting up a guitar, but were I a professional musician, I'd happily pay Perry, Jeremy, Myka, or whoever else a couple hundred dollars to do the job right.
Greg