The bonus he received in addition to his salary was pure 'gravy'.
They're trying to get on board the 'gravy train'.
a 'gravy' boat [=a container for serving gravy]
(..) you were a scullery maid? What if he thought you were this total babe? What kind of total babe would be dressed like a scullery maid? I smell like gravy. -What if we made you a new outfit? -I'm thinking... Jumpsuit! What's the point of a jumping suit if I still have this hair? (..)2016 Trolls