Long ago, I used to buy watches to fix and then sell them you-know-where. Being a technically-minded guy, I developed a method of pricing that purported to find a price that stood a good chance of selling without losing (or making 😉) too much money. So, for a particular model of watch, it involved analyzing past sold prices to come up with a selling price. Today, while scrolling through my blog, it occurred to me that the method could apply to camera stuff - so here's a link for your enjoyment:
tcktek.blogspot.com/2011/09/watch-valuation-hard-way.html
As I read it some 14 years after publication, understanding did not jump right off the page - so I stand ready to answer any questions or to defend myself if told how wrong it is ...