I can calculate the motions of heavenly bodies but not the madness of people, "said Sir Isaac Newton in 1721. He was referring to the greed of equity investors in London at that time who lost later heavily.
Greed is one of the common trait found in human beings. It is not only shown in terms of accumulating money, by the tendency to accumulate, to hoard and possess itself is the result of greed. Greedy people want to collect everything -- from money to things to people to memories.
They want to stuff themselves inside outside so that they don't' have to face emptiness. Look at people's homes, they are so cluttered!  Rooms are stuffed with unnecessary gadgets, things, furniture. People cannot throw even old unusable broken equipment.
Just the other day I was looking at a photographic record of Sigmund Freud's house. It really is  worth studying. The whole house seems to be so cluttered with things that one wonders how Sigmund Freud managed to live in it.
To live in such a room is indicative of his mind -- the mind of greed. No space in the room indicates his inner state, there is no space there either. Sigmund Freud is a very knowledgeable person. He was living as if afraid of emptiness because he was very afraid of death. And death means emptiness.
Osho looks at greed as an existential problem. Greed is not a feeling, nor an emotion greed is a deep hollowness in the being, which people want to fill with outside things. They are not conscious about it though.
Osho has analysed this trait beautifully, " Why do you accumulate so many things, why do you accumulate so many ideas? Just to go on feeling that you are full. People eat too much just to feel full, people are constantly moving from one crowd to another crowd. People are members of religions, members of clubs, members of political parties…a person keeps himself occupied, so that he never becomes aware of the inner emptiness.
"Inner emptiness seems to be like falling into the abyss. So people go filling themselves with anything; that is greed. Greed has nothing to do with money as such, anything that you go on filling yourself with is greed.
Greed can only disappear when one meditates, for meditation fills the inner emptiness. One is so content that the need to stuff it with something  else vanishes.