I feel like the issue with vintage Breitling is that you just don't see very many good examples show up on the secondary market very often (exceptions being the 806).
I personally have been on the hunt for a later Chronomat 808 with lume plots on the inside track. I've only seen 1 show up at a dealer in the past 18 months I've been looking. Then you consider how often a clean TopTime 810 shows up. Maybe 1-2 every quarter? In fact, I think most of desirable vintage Breitlings (765AVI, SuperOcean 2005, etc) have really only come up for sale through dealers. I can't think of very many private sales so far this year.