All my tools have paid for themselves in the form of saving on labor. Around here labor rates are $90-120 an hour.A good mechanics set of tools costs thousands. Then you have the testing equipment, adjusting equipment and ...and...and
FYI, I still have a '96 Honda Accord that I bought new. Right now it needs new tires, new front axle boots, 90k major maintenance. I got an estimate from an experience local mechanic: $400 for Michelin tires, $280 for the axle boots, about $350 for the maintenance. It also needs front struts and a battery: maybe a couple of hundred more, installed.
You do the math. And this is a car that really, has never broken down or not started, ever.
Do I have the money/knowledge or time to find/buy all the tools (maybe some new, some used), learn about the repair, price/buy all the parts, take apart an old car w/o a lift, install everything perfectly and then trust me and family on the freeway at 70mph? Well, I do have the time and the money, but I won't spend on tools that may only be used once.
Yes, a professional mechanic will have thousands of dollars worth of tools. But the typical shadetree mechanic doesn't need all those tools. Most of the work is simple things like oil changes, spark plugs, brake jobs that really only need the basic tools. It's not like he's going to be rebuilding an engine.
It is important, however, to make sure you have the right tools.