Cost an Arm and a Leg

Something that is very expensive

Eye Candy

Something or someone that is attractive to look at but not necessarily substantial

Sky Is the Limit

There is no upper limit to what can be achieved

Long Story Short

Used to indicate that you are giving a brief summary

Catch Someone with Their Pants Down

To discover someone in an embarrassing situation

Storm in a Teacup

A lot of commotion or fuss about a trivial matter