Answer:
The only thing I can think of is that they both have a very long term view of how problems come to be and are treated. Psychodynamic quacks believe that problems are a result of early childhood experiences and took many years of continuous experience to become what they are. They also believe that it will also take many years of continuous experience with psychoanalytic therapy to reverse them if at all. Biological approaches hold that genetics and physical structural neurological abnormalities (this is a HUGE fallacy) are the principal contributor to mental illness and that other factors are smaller contributors. Because they believe that these lifelong matters cause mental illness, they believe in LONG TERM biological treatments such as drugs for life. I guess I could also say that both can be quite profitable to the practitioner.