It's worth whatever people are willing to pay for it.
MS is technically giving the game away for free if you buy an XB1.
Plenty of people who paid $60 for it are getting their full value out of it currently as they marathon the game.
Is it missing some things one would expect out of a high profile, big marketing budget, hardware selling title? Hard to argue with that, but Titanfall is providing the exact kind of online entertainment consumers are willing to pay $60 for.