Movies have much, much more replay value than games... so again, it's not the same.
And the scenario you were suggesting earlier was that one would be interrupted by a Dorito's commercial when they get to a Dark Souls boss battle, and say to themselves, "wow, I should really drop the $60 on this now." Which just isn't going to fucking happen. They're either going to finish the free version of the game and never think about it again, or they're going to get fed up with the ads and stop playing... but this sort of set up will almost never result in a sale, let alone at $60. Why would it? If they didn't see the point of the investment earlier, why would they several hours later when they're playing a free game they don't ever have to pay for? The cheapskate mentality is a palpable thing.
No matter how badly you want to believe games are analogous to movies or music, they're not. The pricing, longevity, and replay value are all completely different; making reasonable comparisons as far as this goes impossible.