Cherrybim, you may be confusing cause and effect. Rebbes and gedolim may have come to NY BEFORE it got to the point that it is today, not the other way around.
Also, your point may illustrate why NY has become so expensive – the more rebbes/gedolim/institutions, the more people want to live there. The more people want to live there, the pricier the area.
That’s a simplistic economic model, for sure. But it doesn’t go really far beyond supply & demand, my friend.