Stephen Diamond writes in Psychology Today back in 2009:
Greed, like lust and gluttony, is traditionally considered a sin of excess. But greed tends to be applied to the acquisition of material wealth in particular. St. Thomas Aquinas said that greed is “a sin against God, just as all mortal sins, in as much as man condemns things eternal for the sake of temporal things.” So greed or avarice was seen by the Church as sinful due to its overvaluation of the mundane rather than immaterial or spiritual aspects of existence. Avarice can describe various greedy behaviors such as betrayal or treason for personal gain, hoarding of material things, theft, robbery, and fraudulent schemes such as Madoff’s, designed to dishonestly manipulate others for personal profit. Where does greed originate?
Both greed and gluttony correspond closely with what Guatama Buddha called desire: an over-attachment to the material world and its pleasures which is at the root of all human suffering. Greed is about never being satisfied with what one has, always wanting and expecting more. It is an insatiable hunger. A profound form of gluttony. Where does greed breed? Paradoxically, greed really arises from too little inner selfishness. That’s right. Greed grows from ignorance (unconsciousness) of one’s self. Addiction is a form of greed. Addicts always want more of what gets them high, gives them pleasure, enables escape from anxiety, suffering, themselves. They greedily crave that which their substance or rituals of choice provide, be it drugs, sex, gambling, food, pornography, internet, television, fame, power or money. We all have our personal addictions: workaholism, rationalism, shopaholism, perfectionism etc. This is our futile attempt to fill a spiritual and emotional emptiness within, to gratify some long-buried need, to heal or at least numb some festering psychological wound…
Read more here.