The iTunes Store is re-emerging as a venue for big pop stars, including Taylor Swift, to hawk collectibles to superfans and bolster their chart positions (Tom Matsuda/Financial Times)

Tom Matsuda / Financial Times: The iTunes Store is re-emerging as a venue for big pop stars, including Taylor Swift, to hawk collectibles to superfans and bolster their chart positions — Record labels and artists including Taylor Swift and Ariana Grande are using the throwback music store to…