I'm a member of a number of different forums, and a moderator on one of those. All of them have some version of the EE, and they all seem to have the same pattern.
People list things, but the question is why? If you want it to sell, the key is to have the right price. If it aint selling, then your price is too high.
The problem with forums though is that they are full of people with a passion for that forum's interest. When you have a passion for something, you will naturally value it more than the average person will. It's that passion that makes us think our crap is worth more than it really is, and so we list the price way too high. When it doesn't sell, we blame the crowd - a bunch of idiots who don't know value! We say.
Across the board I always use the rule of thumb that any used item is only worth 1/2 of the new price - the price if you bought it new. Then you can adjust up or down a little based on condition. So a used item that is truly in mint condition - list that for about 60% of the new price. If it's used and in decent condition, Keep it right at 50%. If it's used and looks like it, better drop to 40-45%.
Often people balk at that rule of thumb. They get all indignant and offended, upset that I would suggest that they should sell their precious mint condition used thingamabob for only 60% of the new price, when they had in fact intended to list it for 90% of the new price and try to seal that deal by boasting you could "save the tax!" . They get mad at me for suggesting the lower price, but a month later when their item still hasn't sold, sometimes they get the message then.
I've almost always followed that rule of thumb, and everytime I have i've sold the item the same day.
I have a high quality impact driver for sale right now that I won in a contest. It's brand new, never been used, still in the box, so I thought I might be able to list it for more. So I actually did list for 90% of the new price and boasted that they could "save the tax" ! Fat lot of good it did, i've had that listing up for a month and not had a single bite!
When buying used, you have more risk. If I buy new from the store, and something goes wrong, I can return to the store and get it made right. No such luck with used sales, so when you buy used you necessarily take on all that risk. That risk is what makes the item worth only half of the new price.
One last thought: on the forum I moderate, we don't delete the sold listings. We just add "sold" to the end of the title, and close the thread. That way all those sold threads remain as a record of what items actually sold and how much they sold for. If I go to list an item, I can first do a search and see how many items like mine have sold in the past and what they sold for, and that gives you a real helpful idea of what I could list mine for.