QUOTE(Kalashnikover_Rebbe @ Oct 25 2007, 02:43 PM)

That's not the point, the interest is just incentive for the rich people to loan money in the first place.
Yes, but the incentive has value and that value is well calculated. For instance, when you buy a corporate bond, you are lending money to a company.
The price of the bond will depend on these factors:
1. The risk free interest rate (e.g. treasury curve). This is the baseline you want to receive, if there was zero risk (as the government issued securities are assumed to have). This should hopefully take care of inflation, which is already an incentive for investing.
2. The credit spread of the bond. This is the spread of the credit risk of the security relative to the risk free securities. A given company may have multiple bonds issued with different credit spreads - they will be in what are called
"tranches".
Given the rate r1 from credit risk, and the risk free rate r2, R=r1+r2 will be the interest rate you want to get from your loan. [You will then calculate the discounted present value (using R) of future coupon and principal payments, and that will determine the current price of the bond].