This is December. Despite the weather, it is a prime tourist season. On top of that, business travel to NYC is near an all-time high. $350 for Hilton in NYC is not unexpected, but you may be able to push for something a little better.
BTW, the New York Hilton (6th & 53rd St) has IMHO the best Executive Lounge on the 44th floor; is very busy; has slow elevators and one usually out of service; clean, fresh guest rooms. I agree with Adam, it is a terrific property with excellent location (now if only they can have all the elevators running at the same time).
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He who dies with the most miles ... is dead.