If a business charges more for a product than the cost to make it, how is our economy not inevitably doomed for debt?
To continue your example: 
Resources (including labor) cost $x$, product sells for 4$x$. The fat cat business owner makes 3$x$. What does he do with it? If he spends it, for example plays golf or gets his hair done then the people providing those services get the money. Thus there need not be debt, the hairdresser can use these earnings to buy the product the fat cat's business was selling. The usual water analogy is of a circulatory system: water (money) flows from one vessel to the other.