For many users entering DeFi, the first number they notice is APY. Platforms display it prominently on dashboards, protocols compete to advertise the highest yield, and investors often move their funds toward whichever opportunity promises the biggest percentage. At first glance, the logic seems simple: higher APY means better returns. But in reality, this assumption is one of the most misunderstood ideas in decentralized finance. The truth is that the highest APY is often the least sustainab...