It is S$50 more expensive than the Apple Wireless Keyboard (S$98) because it now comes with a Lightning cable and a built-in battery.
Finally, Apple decided to ditch the usage of AA batteries by including a built-in battery and using a Lightning cable to charge it. This gives it better battery life and makes the keyboard much lighter.
They did the same thing to the Apple Magic Mouse 2. But at least for the Magic Keyboard, you can charge the keyboard and use it at the same time unlike the Magic Mouse 2.
The design has been change as well. The bottom now lays flat on the tale which gives it more stability when typing as compared to the Apple Wireless Keyboard.