A lot/few of the guys on this forum do their own work because they know the only way to know 100% that it is done right is to do it yourself. There are no excuses. No one else to blame.
It really sucks when you take it to the "professionals", and it turns out substandard. The pro's are doing it for money, and faster they can do it, the more money they can make.
The DIYer is doing it to make sure it is done right. Different metric. And to save a few bucks...but that doesn't usually include paying yourself for the time. I know with all the time I spend on my vehicles, my time works out to be about 5 cents/hr.
That's why I don't work on other peoples vehicles.
The time gets eaten up putting parts together, measuring/testing, pulling them apart, measuring again...repeat. That is why racing engines cost so much. You have to pay pro's for that time.
Oh, and the sense of accomplishment. It's hard to beat that feeling when the engine you've been labouring on sputters/roars to life for the first time. It does wonders for your self worth...or maybe it's just me.
My 6.9cents/hr.