Standing Wolf has it right. Most gunsmiths got into the business as an outgrowth of a hobby and never cared about the business aspect. When I am asked about going into the business, I start talking about taking a business course, complying with zoning laws, keeping books, making tax payments, getting capital, and so on. The questioner almost always says that he won't bother with "that crap", he just wants to work on guns. But if he doesn't bother with "that crap", he will fail in business and just might go to jail, not for violating a gun law, but for failing to observe other laws.
Believe me, more than a knowledge of guns and an FFL is needed to be in the gunsmith business. Worse, many do not even have the knowledge. Since gunsmith schools cost money, it is easier to hang out a shingle and gain knowledge by ruining customers' guns.
When I worked (primarily) as a pistolsmith in a general gunsmith shop, I tried to have the work out in a few days, provided I had the parts. In one case I had the work done before the guy left the shop, but I let him wait a couple of days to justify what I thought was a fair price for the job. But there are delays on complex jobs; no one would want a .45 accuracy job done in a big hurry.
Also, some parts and equipment suppliers give a discount for a large order, plus shipping eats you up on small orders. So the shop waits until they have a two hundred dollar order before sending it off. The customer waits and is told the parts are on order. Sure they are, and the order they are on is on the desk. He blames the delay on the parts place.
The customer is not always free of responsibility, either. When having a job done, know what you want. A few minutes getting things straight will pay off in not having the wrong thing done and having to do it over.
Do what you can yourself. At one shop, I asked the owner why he took in a shotgun that needed a box magazine, rather than just giving the customer the address of Gun Parts. He said he made a couple of bucks on the magazine and didn't really care if he kept the gun forever while he had it on order (see above). Needless to say, that guy had a lot of frustrated customers, a lot of very dusty guns in the rack, and a lot of paperwork he didn't need to do, all for a few bucks.
Jim