[bogomipz]

It's because Astoria/LIC has seen a large population density increase. Look at all of the new high rises along the East River and Astoria because its slightly cheaper because it doesn't have the cachet of Brooklyn.

It's also worth noting and evident on the map I linked to that when people talk about Brooklyn in many contexts(uber, hipsters, nightlife etc.) they are only ever talking about a small subset of Brooklyn which is strip generally nearer river that extends from Greenpoint to Redhook. They are almost never talking about the majority of Brooklyn - East New York, Dyker Heights, Canarsie , the Flatlands etc. Brooklyn as the city's largest borough is huge. Brooklyn is actually the 4th largest city in the U.S.