Well, all a $15k a year tax bill means is that he makes a pretty good profit, or the shop property is worth a WHOOOOOLE lot. The cost of the employee, like ChevyFazer pointed out, isn't really a cost. I work for a friend who owns his own auto shop, and I point this out to him all the time. I cost him $10 an hour, and he bills at $75 an hour. If I finish a job at billed time, I just made him $65, plus whatever profit he made on the parts I installed. Even if I take double the time, he's making $55 on every billed hour. An official employee making more than that, and with payroll taxes and such, isn't that profitable, but they're still making you money.
The tools are a cost of doing business, they either let you do the job period, or let you do it faster, so you can make more of that sweet profit. If you charge less money, but still make money, you'll attract more customers and make those tools pay for themselves faster. Who am I gonna pay to put my tires on, the shop that charges out the yingyang and makes a bunch of profit, or the one that has a reasonable price and only makes a few bucks? And while I'm there, I'll probably buy more stuff, too.