You don't know what you're missing.

You don't know what you're missing.には文字通りの意味しかありませんが、文脈に沿ったそれなりの解釈になります。0:30 you do not know what you are missing. このソースを知らないのなら、自分がどれだけ損してるかわからないでしょうね。

https://www.youtube.com/watch?v=3gTNstioQ5o  32:19 you don't know what you're missing! この眺めは見なきゃ損だよ。
https://www.youtube.com/watch?v=rv6T6YuSXOA  0:55 you don't know what you're missing. 後悔しても知らないよ。

4:35 and if you've never done deep fried corn, you're missing something out of your life. = you're missing out one half of your life. you're missing half of your life. 人生の半分を損してるよ。

Deep Fried Roast Beef by the BBQ Pit Boys

練習問題解答
a-500 you don't know what you're missing
b-3203 you have no idea what you're missing