I look at it this way--I can usually get new OEM parts at less than what a shop would charge me for reman or knock-off parts, and any tools that I need end up costing less than the labor at shop rates. I end up spending less than I would at a shop, have the tools for next time, and I know the work was done right, on my schedule.

Oh, many auto parts stores will rent or loan (for free!) tools that you may only need once. Around here, you can even borrow the OBDII code scanners for free.