Any seller can sell anything to anyone they want for any price....

Any seller can sell anything to anyone they want for any price. There are "Dark Pools" where many of these stock trades are done. All sales of stock in US have to be registered with an exchange that caries the stock. Usually by end of day. A few exceptions allow slightly longer periods, Many of these sales are registered at close. Which causes some of the strange activity you see at close. These trades can be just at an agreed price. Or a price based on a % of the average price durring a certain periods. Sorry only know US rules most countries are simalar.