Yep I did realize the $1B issue too. Am building a way to dynamically set the exit valuation, probably next weekend.
As for dilution there isn't really a good way to factor that in. I still believe that using the BSM options model is a much better gauge of value than what most people use so hopefully it provides some benefits there.
Had enough friends asking me about ways to value their startup offers that I created this site. It uses the binomial options pricing model to calculate the value of stock options to give you the fair market value of your offer.
Tell me if its useful or missing anything, any feedback is welcomed!
Given stock is the best way to motivate executives, when the guy on top is giving all of it away you know where the stock price is going.