Accuracy of used market pricing on Chrono24

[gamingdoctor]

The common sentiment here seems to be that the pricing on Chrono24 is inflated, and that lower prices are negotiated off the website. As I'm looking to buy a used watch (strongly considering a 116509) in the next few months, is there any way to tell what prices watches are actually selling for?

I'm aware of watchcharts and moda, although the former doesn't have good data on more unique models and moda's data can be quite sparse. Ebay sold listings are another, but I can't imagine there is a lot of high end trade on there.