Such option could easily increase demand, be more cost efficient and higher margin and be highly dependent on market reach , which makes it very difficult to replicate.
And i'm sure UBER has some data to demonstrate this and other attractive options to investors[1], which make it much harder for us non-insiders to truly evaluate UBER.
[1]A similar example is the nest acquisition, which raised many eyebrows and guesses, but it appears they had a "secret" way to monetize their service - selling demand response services to utilities.