What is an appropriate response when someone tells you to "take it easy"?

When someone says “Take it easy!” as a form of goodbye, what is the correct response to that? It seems lately, for some reason, a lot of people around me have been using this phrase instead of saying “bye” or “see you later,” etc., and I never know how to respond…Thanks? Okay? You too? Or should I just say “goodbye” as if they had said goodbye?

Furthermore, why can’t they just say “goodbye” like a normal person, thereby eliminating my confusion?...arg!