The server's economy is geared towards player interaction. Players can buy and sell items to each other and also pay for services/jobs. There is a town/server shop that serves as an economic baseline, but note that you will generally get the worst prices at the town shop - it's almost always better to deal with players, either directly or via player-made shops. In this way, supply and demand is driven almost completely by players.

/balance - check how much money you currently have
/pay <playername> <amount> - send money to another player
/worth <itemname> <quantity> - check the market worth of an item; this is useful in determining how much to sell or buy an item for

Shop tutorial video: https://youtu.be/BKhTNKMKb7M?t=734