To start with, as owner of Speedmaster101 says, it is his guide, to be used as a tool for helping with one's owns research and certainly not a definitive price list.
And even if it was definitive (it isn't), there are so many other factors. Are you a buyer or seller in a buyer's or seller's market, are you wanting to sell quickly to a dealer or trying to sell it in an auction, what time of year is it and how soon do you want to sell, etc...
People get fixated on the dollar amounts in the chart. I think the primary benefit of the chart is in establishing a system for describing a watch from poor to excellent. The specific dollar amount fluctuates, but the condition is fairly stable. While it's difficult for a few people to agree on condition of a particular watch, generally a large group will be able to come to a consensus, which is why it is helpful to seek input from a larger group who are familiar with a reference.
People often ask the dollar amount for a watch value when they should be asking about condition of a watch. The condition strongly influences the dollar value, and it's easier for others to offer a definitive opinion on a condition than to offer a price, which can be so subjective.
Even if we are pushed to offer a price, it's easiest to ball park a price for insurance purposes, for people who just want to know what they have. The next category are the buyers. For buyers, we can say you should pay no more than a certain amount. But for sellers to ask how much to charge for their watch, I think it's an unrealistic request.
And finally, Speedmasters aren't mythical, they are iconic
😁