It's horses for courses...
I would be confident of buying a car, and being able to fix up whatever needs doing, without issue, as I can either do it myself, or know people who do.
I wouldn't try building a PC. I have friends tell me all the time, how they built this super duper computer, or knocked up a cool website, for a few $$. I wouldn't try, because I don't know how, or who.
People hear of how someone build a cool car cheap, but unless you have the contacts, or skills, it isn't for everyone to contemplate.
You can't put $$ limits, or time limits, on a car build.