Essential is relative meaning whatever living situation you would deem appropriate for a person to live in. It is ultimately a relative term. Those with more, like those that don't think $600 is a lot of money, should higher the bar for what they deem is essential, especially considering they have much more in comparison.
You're right. It is abhorrent that cancer patients should have to pay exorbitant fees (or any fee) to stay alive. We shouldn't do that in society and instead accept some form of socialized medicine IMO. I mean I don't see the point of bringing that up though. that doesn't justify taking advantage of people's misfortune that are even less fortunate than you. I'm not arguing with you that you shouldn't get paid for your expertise. You definitely should. I'm just saying what I believe should be the obvious. When you see someone that is going through some unusual misfortune (especially if you they are less fortunate than you) and they have no choice but to rely on your services (such as in a crisis where resources are limited and you become the monopolist), don't just think about how you can gain extra money out of it and instead think about the value in helping those people.
I don't mean that as a personal attack on you that you do so. But from what others and you have said so far worries me that you might.