First off, while the DSM is useful in the treatment and diagnosis of mental illness, it is absolutely useless when it comes to studying the mechanisms of mental illness. The DSM is just as much political, as it scientific. People with current diagnoses fight to have their diagnosis stay in the DSM in some form, even if research suggests that specific form no longer makes sense due to current understanding. Often, a mental illness is considered as such only if the condition degrades one's quality of life, regardless of whether the understood mechanism is currently present for an individual.

I think the original post was meant to convey that perhaps the mechanism involved in getting rich/greed is similar to that of addiction, but the outcome isn't considered detrimental to the individual's quality of life, and so we as a society do not label it as mental illness.

Neuroplasticity refers to the changing of connections between nerve cells in the brain. Many mental illnesses seem to be related to, at least in part, a slightly differently wired brain. CBT acknowledges this, and attempts, in theory, to use behaviour to coax the wiring back toward a more typical wiring