The adjective expensive means high in price, like the expensive basketball sneakers you had to work all summer to save up enough money to buy.
Expensive comes from the 1620s, when it meant "given to profuse expenditure." Back then, it was the people doing the buying who got called "expensive." Now it's the costly things they buy or take part in. For example, sailing is an expensive hobby. If someone tells you, "I have expensive taste," it means that person likes things that cost a lot of money, whether they are purchased or just admired from the shop window.