Why are some books on Confucius Old Books Online so expensive?

Although the books on Confucius' old books online are all old books, they are also divided into different types. One is to sell my old books online without reading them. This website is equivalent to a flea market. The second is books that are temporarily out of circulation or have been removed from the shelves, which can be found on this website. The third kind is ancient books, which are rare books with great historical value and collection value. Some prices can even reach 4.556 million. Therefore, the first two books are sold at a discount because they are used books, that is, the price is around 15 yuan, while the latter is more valuable and naturally expensive to sell, so the price difference is quite large.