Must the UN stay in Manhattan ?

This opinion piece in International Herald Tribune caught my eye. Is it necessary for a cash-strapped organization whose mandate is to preserve world peace and fight poverty to occupy one of the most expensive pieces of real estate in one of the world's most costly cities?

Having worked with NGO's before , I have seen from close how most of them strive to keep their overheads (costs) very low so that the majority of the donor's money go to the help the cause .Shouldn't the UN be following the same ?