Why? because that was return on your ad.
CPM? Just don’t worry too much about it, except if you feel that it’s very high because of seasonality, maybe you don’t want to do ads that time.
CPC? Is a function of your ad and the landing page
CPA? Keep average attribution window in mind that the customer acquisition is based on attribution window.
I will do a little video on attribution window because it’s a complex enough set the subject, which deserves its own video.