I upgraded a 1991 Schwinn Paramount frameset to all Shimano 105 5800 11 speed right after that group came out. Since I had to buy bars, stem, wheels, saddle and other things for it, I didn't save myself any money that wouldn't have put me in at least a new 10 speed Tiagra equipped bike for that day.

Upgrading that old bike did let me get some experience with DIYing the new components which was good since I was pretty much still in the days of 6 speed freewheels, single pivot rim brakes and downtube friction shifters.

What upgrading that bike didn't do for me was get me a lighter bike. So I wound up with a 22.5 pound bike which some say isn't bad. But it's not great, especially if you ride long and in rolling to hilly terrain. The new 10 speed Tiagra bike I could have gotten then will probably have been 19.5 lbs. or so. Sure, If I'd gotten better wheels and Ultegra or DuraAce components, I might have been down to that weight with my build, but then I'd have spent money that would have gotten me a even better bike for the day and probably be sub 18.5 lbs.

If your frameset weighs 6.5 lbs, you won't cheaply build your own sub 21 lbs bike. IMO!