Half the cost is in the battery the other half is in the smart circuit contained in the battery case that smart chargers your battery, monitors the cells, keeps records off the cells and sends cell info and data to your drone so it know how much power to use and when to return home.
Is why it's called a smart battery.
i've come to accept that when a company is prepared to replace a faulty device for free, they are going to charge more. if you have a faulty battery, you can send it back to DJI, and they'll replace them. so expect DJI to add a margin in the pricing to cover that sort of thing.
Have you ever bought a smart lithium-ion or lipo battery for anything? $42-$50 is a bargain. The battery for my camera is $75. The one for my lawn mower is $220.