A PICTURE OF A RICE CAKE 그림의 떡
This expression is to do with MONEY. It describes something that you want but can’t afford, something that is out of your reach. Just a dream.
So you see some Jimmy Choo shoes or a Louis Vuitton handbag that you like but of course they are far out of your price range. So you lament how they are a picture of a rice cake because you will never be able to afford them.
Just like pie in the sky, a picture of a rice cake won’t fill you up if you are hungry. It’s just a picture and just a dream.