When an annual gift exchange is lopsided, it will stay lopsided forever.
Let's say you give your colleague Jenna a $15 gift certificate and in return she gives you a $25 gift certificate.
You make a mental note of this and remember to give her a larger gift next year. But Jenna too remembers the lopsided exchange, and next year she downshifts your present into a $15 gift certificate.
There is no solution to this problem.