Similar to the art of honesty, you have to look at this as a long term life-choice.
Let's say you dealt with two people. One, looked out for you. S/he was kind, helpful, honest, and created a win/win situation. The other, got about 6% more out of you, and you felt like it was a grueling experience.
Who would you talk about highly, deal with consistently, and support? Who would you be inclined to help, or send business to?
Magnify that over a decade, and you will see why those who create win/win deals always out pace those who do not.
If someone beings you information or product which makes you a fortune, reward them. Not only will it encourage them, but everyone who hears your generosity as well.
Plus, it feels good.
Recommended Reading: The Secrets of Power Negotiating
Sensei Ono, Shinka Martial Arts
How could you best encourage a blogger to blog?