alt Hacker NewsA good haircut takes about 30 minutes. So if the barber is getting $20/cut that's $40/hr gross max assuming he's booked solid every day (most are not). From that they have to cover the rent (or property tax, insurance, and upkeep if they own the shop), utilities, scissors/clippers and other instruments, consumables, their own self-employment tax, health insurance, and retirement. That doesn't sound like it would leave much.
30 minutes? There's a ton of men with a simple hairstyle just going for a quick trim, a competent barber should be able to handle three or four of those per hour easily.