Why does the discount rate here different from what I thought a discount rate is? Why does it take into account the weighted cost of capital? I realize this is a CAPM equation... but why does it intuitively make sense as a discount rate? Why isn't the discount rate just the risk-free interest rate? The discount rate. This is the rate at which you discount future cash flows. The discount rate is by how much you discount a cash flow in the future. For example, the value of $1000 one year from now discounted at 10% is $909.09. Discounted at 15% the value is $869.57. Paying $869.57 today for $1000 one year from now gives you a 15% return on your investment. The discount rate is essentially your required annual return on investment. http://www.investopedia.com/university/dcf/dcf3.asp#axzz2ARkx27dn

Istead of askng here where you'll get a lot of random people guessing, you should get a good corporate finance text book. They are pretty easy to read and probably cheap.