I'm a mixed bag for thrift. I own no 10 or 11 speed or brifters. (DTs work, are universal, cheap and always survve routine crashes unscathed. 9 speed wheel come up regularly at good prices.) I have one new derailleur on my 3 geared bikes. I ride mostly fixed and that saves a lot of money over the long run, although the 15 or so 1/8" track quality cogs cost a lot. I ride good tires because I like good performance and road grip. Patch my tubes. Build my own wheels (and rebuild the wheels I buy at >=$100). Regularly go to the two shops with extensive used parts bins. All my bikes are either from used frames or custom. (3 of each. All but one of my used bikes has a custom stem. Stock bikes that actually fit me are rare and I am no longer willing to compromise on fit.) So I have paid $20, $20, $70, $450, and twice >$2000 for my frames.
I have some parts that have many years/miles of use. My old Mooney has on it now a wheel built in the early '80s around one of my old racing hubs. Seatpin for that bike is off my first 10 speed ever. 47 years old! The Mooney was built with canti brakes as a cost saving measure, and wow! has it! I think the braze-ons cost me $20. About $30 for the Mafac canti calipers, upgraded with Shimano OEM cantis ~mid '80s. Cables, housings andpads, a 2nd set of levers (due for a third). Not bad for a 46,000 mile all weather bike if I do say so. (60,000 for that seat pin!)
Ben