What that means is that those games can have <$15 from me, or nothing. $60 was never on the table. And the games I buy at launch others won't bother with at full price.
The only difference between me and the pirate in your example is that the pirate hypothetically would have bought "some" games at full price if piracy wasn't available, like I do. But that's not an assumption you can naturally make. Some people just don't care about playing games when they're new.
I'm just as inclined to assume that a pirate only buying bargain games would have the same legal consumption without piracy.
For my part, it was not a lack of money, but rather ease of getting the game (when I was directly given an ISO) or because I don't want to wait for a sale, but the game still seems too expensive. I ended up buying two of them (KotOR on a sale and transistor full-price). But now I have a big enough library and I have less time to play, so it's not as appealing as before (and I also have more to lose on my computer).
The study only looks out the count of games and not the dollar amount spent. A non-pirate who buys a $60 game and all the DLC and microtransactions is counted the same as a pirate who buys one $0.99 steam sale game. It does say that sales for blockbuster movies are heavily impacted by piracy.