It's mostly the rent but it's also Amazon.

I recently took part in a commercial real estate search in Soho, probably the biggest shopping district in NYC. The prices in this neighborhood have gone up insanely: one storefront (about the size of a large Banana Republic) recently sold for ~250M dollars, which is obviously absurd. The broker told me that a lot of these stores were taking losses on their commercial leases with the (mis)calculation that the exposure and presence were worth it. This miscalculation is everywhere, you e.g. see the same thing with banks opening locations every 5 blocks. Where the real bubble lies, IMO, is that a lot of the places are going to see competition from online and will no longer be able to justify the losses they've been taking. NYC needs bodegas, bars, and coffee shops - things we can't do online - not Bank of Americas and Banana Republics.