I moved from Houston to Fairfield County 2 years ago. Cost of living calculators to estimate the change in cost of living were low for up here in my opinion. They all estimated 50-55%... maintaining standard of living I've figured living in this area that number is closer to 65%... I got substantially more than that to take the job and relocate.
I'm in Manhattan often and we looked at potentially moving there when we relocated. By my account, I'd estimate you'd need 50-60% more from Fairfield County to live a comparable standard of living in Manhattan depending on where you live. Are you dead set on living in Manhattan or are you open to commuting? Because there are areas like Brooklyn, Jersey City, or Long Island City that are substantially cheaper and ok areas to live in and not a long commute from Manhattan.
Good luck whatever you do. We really like it here. Just know that everything is really expensive, not just rent and restaurants/bars. Trains, taxes, etc. really add up. Also, I'd recommend if you are dead set on living in Manhattan that you do a trial in an AirBnB for a couple of weeks if possible. Even with COLA bumps, etc. you'll likely be in a smaller older space and getting around without a car is more of a pain in the ass than you are probably realizing. Manhattan is a blast, but it isn't for everyone and a lot of times people who think it's for them are wrong... they don't understand how different it is than almost any other metro you'd live in in the United States.
BTW, if your salary is $75k, I'd start the negotiation at $200 if you are set on Manhattan and wouldn't consider moving unless for lower than $175. If you are open to commuting from somewhere like Fairfield County (long train ride back and forth daily), you can probably get by on 135 or so. And it's cool to get creative but not too creative. The difference in cost of living it too substantial not to get the salary bases you'll need to not be poor.