"price" doesn't really describe this concept well. It's more like .. trying to judge the value of your laptop, by looking at what identical models have sold fo

"price" doesn't really describe this concept well. It's more like .. trying to judge the value of your laptop, by looking at what identical models have sold for on ebay. This is where the "supply vs demand" adage comes in. If there's 1000 copies of your laptop on ebay, and one person trying to buy one, then its a buyer's marker - the cheapest auction sells, and the market value of your laptop just fell. But if there's thousands of people trying to buy one or two copies of your laptop, then its a seller's market - the highest bidders get their laptops, and the market value of your laptop rises. So (ignoring deprecation/inflation) your laptop didn't actually change. Its intrinsic value, if any, didn't change. But the market's position towards your laptop did, and how much you believe it'd fetch at auction right now, did.