I hope it'll be $29, because that's near enough to free, and I like the idea that Apple has a financial incentive to continue supporting their existing customers.
Then I will keep using Lion in hope they release a real OS X update sometime in the future for which I would pay play gladly as I've been doing with all the previous updated, because right now Mountain Lion is just a bunch of iOS Apps ported to OS X.
I'm sorry, but IMO the value of this update is $0.
