Why DIY

I know that not everyone can do every job for themselves. I'm actually facing this because I need new tires on my car and I don't have a tire machine to remove the old tires from the rims and to put the new ones on. But, some jobs are super simple and you can save a lot of money by doing them yourselves.
I took my wife's car to Firestone (whom I actually quite like) to get the oil changed (which could do myself, but I have no easy way to dispose of the used oil). As is usual, they check everything and worked up a "recommended services" invoice for me. Not surprisingly, the tires were listed on there, but so, too, was a new air filter. Check out what they wanted for a NAPA air filter:
Now, note that they put the NAPA part number on the invoice. So, I took that number, drove over to NAPA and bought the filter and replaced it myself. Here is the receipt from NAPA:

So, basically, I saved $19.11 by doing the job myself. And air filters are super simple.
I also do my own brakes, shocks, etc. And, I fix a lot of my own stuff around the house, too.
Saving all of those dollars on repairs means more coffee for me! Ok, really it means that I can put those dollars toward other bills.