I have had an impressive run of good luck with FB Marketplace lately, including a 1988 Centurion LeMans with Tange No. 2/Mangaloy 2001 forks & stays, an amazing Specialized Sirrus with full original 105 6-speed for $50, and a really nice full Reynolds 531 1974-76 Raleigh Gran Sport for $60. The rest of FB, meh - snippets of things from a few people I otherwise wouldn't see or hear from separated by a wasteland of political tweets larded up with our tech overlords' heavy-handed censorship. But sometimes you can score a hell of a deal.
Also - don't forget
the Classic & Vintage section's for sale page, there are often deals to be found there!