Make up for the cost by eating plenty
Bǎ běn chī huí lái
[Grammar particle (take)] Cost Eat Return Come
A Chinese friend of mine taught me this phrase, which I find very interesting. It isn't a chengyu though.
Meaning: If you go to a restaurant and have a eat-all-you-can buffet at a pricey restaurant, then you might use this word to make the point that you (and your friends) should eat a lot to make up for the cost.
I gave it the best English translation I could think of at the late hour. If you can think of a better one, please do write me.