It's subjective, since it depends on a number of factors, but the majority of the time if you're paying someone to do it it's most cost effective (for time) to just wipe and reinstall.
The only time I find it's worth a while to try fixing it (and you can never trust it fully since it might have something hidden as a rootkit or in alternate file streams, etc...) is if you're curious enough to spend days eradicating the problem as an intellectual exercise, or the computer has very proprietary and specialized configurations of software that are very particular to a particular user.
Today it's just too commodity to spend more than a few hours on repairing a system. Today home computers are so cheap for what most users do that even if a shop charges thirty or forty bucks an hour to fix systems it'll cost more to repair it than to just buy a new CPU.