There's no two kinds of humans - from each according to his ability, to each according to his needs. The doctors will get free healthcare too, if they need it. Trying to put market value on medical care is inhumane and prioritizes an economic system over human life.
I'm not sure why you're talking about rich people here, but because you brought it up - the accumulation of capital is what's truly exploitative.
Value doesn't come from speculative markets, but from the sum of labor put into it. Rich people realized that if they use some of their capital to provide the means of production, they can skim off surplus value from the workers putting in the labor.
In other words, even though they don't do anything productive to create the value, they still take value that others created. That is exploitation.