Okay, lets go with the facts. If you work a 40 hour week, 50 weeks per year, that equates to 2,000 billable hours. At $20/hr, you would make $40K if you work full time with no sick days, no vacation, and the standard 10 holidays per year. And no benefits except working at home with no real boss (wife excepted).
I quit working about four years ago (not retired since I don't get a pension), but from what I hear, they want to give tax credits to people who make less than $40K. So $40K for a craftsman is not economical.
Figure out what you want to make per year, divide by 2,000 FOR A START, knowing that you won't work 2,000 hours.
I have build three full kitchens and a lot of furniture for the worse customer in the world, my wife. I have many friends ask me to build them something, but with my pace of work they either can't afford it OR I will have to over charge (only in my estimation). Probably cutting myself short, but life at my age is too short to worry about making money. Like many on this site, I make presents and enjoy myself, but you would probably be surprised if you price your work at $100/hr - they would still come!
Good luck
The only thing you should be charging by the hour is high end furniture.Cabinetry is not by the hour.
While having an hourly shop rate for incidental work is great (and that number is way too low), as has been noted already by folks who have been in the business, cabinetry type work is priced more by the job and quite often by the linear foot. You not only have to cover your materials and labor for creating the stuff for the job, but also cover yourself for any time on call-backs and so forth as well as "shop costs" for heat, light, power, machine maintenance, tooling acquisition/replacement, insurance, accounting/legal services, etc. (all that latter stuff is "overhead" that any business has) You pretty much gave that first cabinet away for sure. Remember, custom/production work isn't to compete with box store product prices; it's to compete with other custom makers your clients might ask to also quote on the job. If the client wants box store prices...they are not the client to woo.
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The most expensive tool is the one you buy "cheaply" and often...
IMHO:
You are competing in the wrong market. Small shops can't earn a living pricing their work against big box stores.
My price for that carcass would be $800 and I don't install. I would not have made it with pocket holes and half inch material either though. My labor rate (if I charge by the hour, which I usually don't) is $125/hr with a 2 hour minimum. Incidentally, I don't advertise as all my work has been word of mouth for a really long time. The only way to make quick cash doing inexpensive cabinetry/installs is closets and folks aren't really that big into that any longer either.