The world of auto mechanics is split into two categories. You have the people in the trade because they genuinely love cars and then you have the people who went into auto repair because their high school guidance counsellor said they should. The first group you could identify with as the hackers, the people that take stuff apart because they find it fascinating, and this interest level over a number of years combines to make them rockstars. This is referred to as the 10,000 hour effect on HN. With the other group, they end up doing basic work but never doing the high pay, challenging work. The common slang for this group is "Mouthbreathers" (1).

So there kind of isn't an average non-rockstar mechanic. I will try to answer your question anyway. A person changing oil and doing brake pad replacement might make between $8-12 in Tucson. This worker would not do any engine diagnostics, nor any specialty work like alignment, air conditioning service, or any problems that would be unusual. A surprising number of problems auto shops repair is unusual. Things like "What is that noise at 70 when I hit a bump" which can often be a hard puzzle to solve.

A better mechanic who can use all the equipment could earn up to $1000 per week as a base, but more typically would be paid on a flat rate basis. So you might get $25 per hour flat rate, and you pay would be $25 x #ofhourscharged . The "flat rate" is typically based on Mitchell Time Guides, which was a book and is now a DVD which lists the expected times to do a standard repair. Unusual problems are not covered in this book, which is somewhat inaccurate but is the best the industry has. (Startup idea: crowdsourced auto repair times).

Specialized skills can get you more money, like any other business. If you are fantastic at transmission repair, or at engine diagnostics, or at solving diesel problems, then you can almost set your own rate. I have a friend who could make a few hundred per hour solving engine drivability problems, but I will note that he is unique. He fixed IBM mainframes before turning to cars. He has his own shop, and works by himself. He fixes cars in a day that other shops have spent weeks on before giving up.

Dealership mechanics can make the most money. A few reasons:
- They work on new cars, so nothing is rusted or dirty. No rusted bolts to slow you down.
- they work on the same cars over and over again, they become familiar
- they have warranty work coming in, and recall work
- the dealership charges more per hour typically than an independent shop
- the dealer is forced to buy the latest equipment, and to send mechanics for training
- the automakers restrict repair information from the auto repair aftermarket

Remember that cars are complex systems now. They involve mechanical parts, electronic parts, wear items, user behavior, and you never have enough information to solve the problem. You don't get to see the source code on anything, most of the time you are diagnosing blind. There are no logs to review besides the trouble codes. Trouble Codes only tell you what the opinion of the ECU is, not reality. I sold several million dollars of equipment based on this distinction.

(1)Side note: once (1996) I won a cruise with 4000 other Snap-on Tools people. My ice-breaking question was "How many mechanics do you let work on your car?" with the typical answer being "none" or "just a couple" which is revealing if you consider that on average a Snap-on Tools dealer has 300 customers. So 1% pass the standard of a salesman who visits him once a week.