We paid for a city pass before we left, it's around $130 but it is cheaper to access some attractions. We used ours for Empire State, Liberty Island, 911 museum and a few more.
It's about $30 for a metro pass for the week each. Much cheaper than paying for individual journeys.
There were 5 of us, 3 adults 2 children. We went to Target & Walmart to buy drinks & snacks for breakfast and to take out with us.
Everything is really expensive. We went to a few restaurants, not fancy ones but paid over $150 plus tip. There was a $1dollar per slice pizza place next to the hotel which was useful!
We saved for the last year or so and asked for $ for birthdays etc. The children had $300 each, they came back with about $40 each. Most of it in souvenirs, presents and treats. We agreed to pay for meals, they had to pay for the random ice cream, Slushy etc.
One adult spent $600 ( again we paid for meals) they got trainers etc that you can't get in the UK.
The two of us spent £2500+ between us. To be honest we were having a once in a lifetime holiday so it wasn't an issue.
We took Chase cards as then you don't pay fees on transactions. You also get 1% cash back.
Remember if you are staying in a hotel they expect you to use a credit card to hold some money in case of damages. We got a 0% credit card just for this purpose. Ours was a hold of £50 per night. We went for 8 nights.