I live in NYC, do your research and make dinner reservations if you're trying to go out to eat. If you have a group over 4 people and you're within a month it may tough to do.
Liquor is going to run you $16 - $24 a drink and beers will run you $6 - $10.
If you want to avoid the tourist traps, then just avoid them. Don't drink in / very near times square.
I'd recommend popping around the East Village, Hells Kitchen, and Greenwich to drink.
Some of my favorite bars in NYC thus far are: The NoMad Bar ($$$), Bar Pisellino ($$$), Dead Rabbit, but they may not be the most bachelor party type bar; so do your research.
Definitely hit an NYC rooftop bar, here's a list from the
NY Times. Some others that I've been to are Mr. Purple in SoHo and Refinery Rooftop in Midtown.
All in all be prepared to spend a bit but enjoy the city.