currently going thru a temporary move (within US) to manhattan, i can offer this suggestion. whatever financial number you have in mind, double it.
and i agree, i found there are a lot of illegal sublets, but legal subleases do exist. i guess due to the high costs of housing there, it was not too unusual that i came across places looking to sublet for 1 month (1 day, 1 week, etc). beforehand, i was not aware of the more stringent requirements (beyond credit checks, etc.) for leasing. this might be helpful to get a feel for things -
Metro International: Publications i found corporate housing to be much more expensive; putting the trip over the threshold of 'do-able'.
nugget - is that $300/night? week? i know not a month.
good luck in your quest.