I have been a YouTube Premium subscriber for a few years. It costs me closer to $25 a month. So your $9.99 is more likely a promotional discount price. Best thing about YouTube Premium is that you watch things ad-free (some movies are still ad-supported, but they are few and I usually don't care about them). Also, if watching on a smartphone or a tablet, you can download and watch offline, and programs that you only need to listen and not watch actively, a Premium subscription allows you to keep the program playing while your smartphone or tablet's screen is off or in screen locked mode (e.g., very good for audio books on YouTube). Also, for certain programs that go slow, you can play at faster playback speeds (up to 3x) to save time (or at least not spend too much time on the boring parts).