The U.S. Open likes to sell itself as tennis's most democratic major — take the 7 train to Flushing Meadows, grab a $65 grounds pass, spend the day a few feet from the world's best players. That pitch is getting harder to make. This year, entry-level grounds passes have been showing up on the resale market for well north of $300, and the tournament's own executives, elected officials, and even a hedge fund billionaire have all weighed in on how a nonprofit governing body ended up presiding over a scalper's market.