Oh, that's easy. Just take a look at camera (tele) lenses: https://pixsy.com/most-expensive-camera-lenses-ever/
4. and 5. are cheaper than OPs gold bar example
2. likely was never regularly sold online, and if it were newer it would be similar to 3.
3. might qualify, depending on how the ordering process actually went -> back when it was available I've seen it in camera sellers catalogues, but it was made only when somebody ordered one, so it quite likely wasn't just shipped out without any extra process.