The most expensive areas in Manhattan are generally West Village, Tribeca and Soho.
However, as I always mention to clients, a good buy depends on location and building quality. Just because a property is in the West Village doesn't mean it's hot, will appreciate tremendously etc. "Most expensive" here refers to what you can get for a certain price point. Or the amount of extra renovation you should still expect to put in despite already paying a very high price.
For example, $1 million may only get an old 1-bedroom condo in the West Village. But in another area, it may get a 1-bedroom in a nice luxury condo with amenities such as a pool, fitness center and nice courtyard. To get a 1-bedroom in a luxury condo in the West Village, you may have to pay $2 million. Hence West Village is "expensive."
In addition, most expensive just means on average asking prices are higher. It does not mean the most expensive buildings are in the area. For example, 15 Central Park West and the Time Warner Center, two of the most expensive condominium buildings in Manhattan, are not in one of these commonly deemed most expensive areas.
Here is a compilation from Streeteasy on average price of a 2 bedroom condominium in different neighborhoods. This analysis is condominium focused. Hence it's also skewed by the ratio of new vs old condos in each area.
West Village $3.995m
Greenwich Village $2.60m
Lincoln Square $2.00m
Upper East Side $1.85m
Upper West Side $1.51m
Midtown East $1.50m
Midtown West $1.44m
Ultimately, I think I'm writing this because people have a love for rankings.