The other day when I was at a Zoom meeting with a customer, the account manager did an excellent job presenting our solution and cut them a great deal with a special promotion. The customer was impressed and grateful and promised to spread the good word about the solution to their sister firms. The account manager was very thankful. The customer replied “ hey, you scratched my back and I scratch yours”. I bursted in laughter upon a vivid mental picutre of two monkeys helping each other, while pressing down the mute button. I was then thinking of the counterpart in Chinese of the expression and came to "投桃报李”，but was feeling short on something. Any more "intimate" translations?