This cow's well worth the cash.
There's some story in the background, but the plot is unmemorable. You start with an empty, run-down farm and fix it up with your earnings. You will buy crops, animals, structures and a face-lift to pretty everything up. Every few levels, you'll play a bonus round in the form of a challenging physics puzzle. The relaxed mode is quite short, while the arcade mode is timed and more challenging. The music suits the game perfectly, and is very pleasant at first; unfortunately, it doesn't change at all and quickly gets monotonous. This doesn't really detract from the game, though, and you'll likely find yourself returning to play "just one more level."
All in all, Cash Cow is a fantastic buy. (Played on iPhone.)