Why does Black Jack charge exorbitant fees? Is there a reason why Black Jack charges exorbitant fees for the surgeries and operations he performs?

In the series I often find Black Jack to be inconsistent due to the amount of free surgeries he performs while maintaining a reputation of charging insane medical fees. Are his ridiculously priced operations merely to get his patients to question the value of their (loved ones) life?



Perhaps the only consistency about his fees, besides their high price, is that if he feels he failed he will cancel the fee. The pricing seems totally random and he charges high amounts even for people that appear to be poor. I understand that as an unlicensed doctor he has no obligations to save someone. However, part of my reason for asking is that the reason Black Jack is alive is entirely due to the fact that a doctor took responsibility and saved his life. Normally, people would feel a sense of debt to this fact and try to repay this debt by doing the same in turn to those they meet in life. I don't think as a doctor he needs to give away surgeries or operations, especially with his level of expertise, but doctors are already well paid and it seems outrageous to charge as much as he does. 



Is there anywhere in the manga or anime that solidly explains why he charges as he does, or are there any convincing arguments about this?
I don't believe there was ever a solid statement in the Manga for Black Jack's high prices. However recently I came across two interesting stories in Vertical's volume #2 that might shed some light on Tezuka's intent.

In the story &quot;Granny&quot; , which is about another doctor who also charged a lot and an old woman who worked her whole life to pay off a debt to the doctor, Black Jack says


&quot;I thought I was the greediest man ever.&quot;


This seems like kind of a joke, so I don't think his prime motivation is greed. In fact Black Jack doesn't seem to spend much of his money ( he basically lives in a shack).
Later in the same story he charges the son of the old lady a huge sum, but that seems to be a test to see if the son is willing to make the same sacrifice that his mother did. It's not clear if Black Jack actually charges the son after the son passes this test.


In the same volume there is a story of Black Jack's recovery from his surgery as a child when a classmate donated a piece of skin to save his face. Black Jack   Promises to become a doctor so he can pay this friend back.


These two examples could provide some reason for his fees, but I tend to think that he really just decides the fee based on the character traits of the patient, circumstances, or finances of the requestors to either punish, reward, or test their worthiness.