What is It's All / Everything's Relative?
means that the world is in the eye of the beholder; it all depends on how you look at things; all people look at things from a different perspective and have differing opinions or views about someone, something, etc.
Everything is quantifiable in terms of individual perception.
To him, the new house is beautiful and grandiose in appearance; to me, it's ugly and pretentious. It's all relative, then, isn't it?
You think you're poor? Then take a look at the skid row bums living in the sewers downtown. Everything is relative.