Right now, there is an extreme shortage of components in the world, especially in IT equipment. There are simply no raw materials and capacity to manufacture processors and other computer parts at the required rate, a problem that may well linger into 2022. This means that many people buy all kinds of scarce goods and then sell them expensive second-hand, where PlayStation 5 and graphics cards have been the biggest sellers.
Graphics cards are also used on a large scale to extract cryptocurrencies, such as Bitcoin. This means that many cards that you could otherwise buy for your gaming computer are bought up for other reasons.