The publicity is worth a LOT. But remember, that's not all we are talking about here. How many MORE people are going to try to qualify through FT now that would have without this promo? Quite a few, I'll bet. No, not $10,000,000 in rake quite a few, but even if they send 1000 players this year (and they won't), there's still only going to be a 10-15% shot that the winner will be a FT qualifier and that they'll have to pony up the cash.
What I think is more impressive is that they are giving away 100 Main Event seats for FREE. In order to qualify for the freerolls, you need to play a LOT of raked hands. This promo is costing them $1,000,000. I think they'll make that back with the increased vig in no time...
Edit: Having already won my seat
I'm now wondering what their policy is if I were to win another. Is it transferrable, I wonder? Most sites say you have to play the first one.