earn (one's) corn

To be worthy of the money that one is being paid. I think you should hire the most experienced candidate because she'll definitely earn her corn. I had to fire Kelsie. Quite simply, she was a slacker who didn't earn her corn. If you have a real drive to succeed, you could earn your corn at any company.

If someone earns their corn, they are successful and therefore justify the money that has been spent, for example on employing or training them. New striker, Steve Menzies, earned his corn with a last-minute goal. Managers earn their corn in these difficult circumstances.