A fair bet is an uncertain prospect whose expected yield is zero. A person is risk averse if he never accepts a fair bet.

The intrinsic value of a fair bet is one in which the cost of the bet is identical to the expected after-tax, net cash payoff. For example, if you had a lottery ticket that promised a 7% chance to win $100, a fair bet would be $7.00. If you could buy the bet for significantly less than $7.00, it is a good  bet.