That's a good thing to keep in mind when dealing on the classifieds. I once offended someone by not trading $800-$1000 dollars of scopes and mods for a rifle on the classifieds price under $400.
I've noticed that the owner of an item for sale often puts a much higher value on the item than potential customers do.
Partly because they had paid more for the item than they are asking, and partly because of an emotional attachment to the item which inflates its value in the sellers mind.
Back when I was a newbie becoming interested in astronomy and telescopes, I put some expensive eyepieces up for sale at what I thought was a fair price of about 15% less than I had paid for them new. Someone was thoughtful enough to send me a note about a reputable discount optics vendor which offered the same lenses new at less than my asking price. I was unaware of the vendor before that and sent him a thank you for letting me know.
That's not the same situation as when someone offers a (not actually) 'rare' item for double or more of the item's typical asking price on the resale market. Sometimes I see eBay offers for things like a pound of coffee for 5x times the typical price in the same list with other offers for reasonable prices.
And I have occasionally purchased an item which was double the typical resale price just because I wanted it right away for some special reason and was having a hard time finding one elsewhere.
It all boils down to the same thing. A potential buyer owes it to themselves to become informed about the average value of items in the current market. After that, they can make an informed decision on whether it makes sense for them to pay more than average.
As for the motives of the sellers who offer items at ridiculously high prices, like for 2x or more for something which I could immediately buy somewhere else. I don't much care because I am usually an informed buyer so I don't waste time on those inflated offers. It takes some time and research to become informed on any topic and this is just one more of them.
JP