He's in a 5k person lot. Not Boozle that saw like 50k every year. Even if he had a bunch of small bands that couldn't sell, the headliners he has now are enough to sell the festival out. Why it's not sold out..well that's the million dollar question. Fall Out Boy sold out NYC's Terminal 5 twice in like 5 minutes. That's 6 thousand tickets right there. A Day to Remember sold out most of their northeast dates on their current tour. The NYC venue they're playing at (Best Buy Theater) holds 2100. That was the first of their shows to sell out. Now you throw in Macklemore who has the number 1 song in the nation, Paramore is heavily rumored for day 1 and NFG (also heavily rumored after canceling the Canada show they had on the same day) and you SHOULD have yourself a sold out 2 days.
First, where so you get the 5,000 number?
Second... What exactly is your point? That you don't think enough tickets have been sold yet? Have you gotten inside access and counted the ticket sales so far? In any case, having a bunch of 2002 nostalgia acts that haven't been relevant in 10 years sure as hell will sell way, way fewer tickets