Something of interest, the Founding Fathers used greed to their advantage. That is why it is a capitalist society.
Don't misunderstand me, they were Idealist as well. They believed that all mankind have good in them, but they understood that you will not get people to work their best just for the greater good.
To work hard and to put your best in the work for the greater good is a wonderfull idea and works brilliantly on paper, but unfortunatly it requires a great deal of moral and mental strength to do that day after day; and that strength cannot be found in great abundence in any country in the world at this time.
The Founders reliezed this and also reliezed that if you offer a reward for the work, they are more willing to do the work. They also knew that if you give more incentives to work harder people would be more willing to do it. That is why capitalism works so well, it is a group of people who are working together for their own personal gain and striving to do better because they know that they will recieve better rewards. Those that work also relieze that if they don't do a good job while someone else is doing a better job for the same price, they will be dropped for the better worker. Same goes for companies and products, if there is something or someone else who is doing a better job for a similar price those who are paying for it will go there. It is all similar to how the laws of supply and demand work.
In contrast, if the people are being paid the same price whether they are doing a lousy job or a brilliant job, they tend to become discourage and just do an okay job because no matter what they are being paid the same. An example of this is communist Russia (no I am not prejudice, it is just easier to see with them as an example), the products that came out of the factories were crap because it didn't matter how good it was they were still paid the same no matter what, as long as they worked.
How this applies to doctors is that they put in A LOT of effort and money to become a doctor, hence why here in America they are paid more. If they weren't paid more far less people would be willing to put in the effort to become a doctor. There would still be those who wanted to help people, but the majority of people who could be great doctors wouldn't be willing.
As an example of people willing to do things for a reward let me make an example: Who here would be willing to take a monkey to prom, and enjoy it? No one?
What if I offered to pay you 100,000 dollars? How many would be willing?
what about 10,000? Still takers?
1,000? I still see a few hands
100? I think i still see several hands in back
What about 5 dollars?
If you were still willing to do it at 10 cents I appluade your, ahem, extreme individuallity.
Edit: The only two motivators in life; Fear of loss, or Hope for gain.