How does companies earn money for investment when someone else bought from the shares they sold to others?

For example if X person buys 100 stocks from a company for $100/stock. That adds up $10000 for the company and therefore they earn it. However if X decides to sell the same 100 stocks for $200/stock and Y decides to buy it and makes it 20000 for X however that leaves the company without any money. Then how do companies make from stocks?