I think $250 - $300 would be very reasonable for a "complete" overhaul. I just bought a $100 vintage MTB Bridgestone off CL. Not expensive. But I stripped the frame naked, and put in new BB, new crank, new cantilever brakes, new stem and handlebars, new headset, new saddle/seatpost/binder, overhauled even the thin copper bushing spacers in the Deore XT MT735 STI brake/shifters. Rebuilt wheels with new spokes and overhauled hubs. Took me an hour or two each evening for almost 5 days. And my hands, despite latex/nitrile gloves, still got grimey. I love to tinker with bikes. But still, 7.5 hrs is lots of labour. If you have the time, tools and gumption, yes, it's great to do. But a good shop charging a few hundred for labour is still a good deal if time is worth money to you. Unfortunately, relative to the value of the actual bike, it may not be money well spent. It might be more worthwhile if you had a custom fitted bike frame with very high value and highly functional components.