What #1 said.

I've done the reverse into London several times. It isn't that expensive, but the weather can be cold and windy. NY has a higher chance of being really cold. But its doable.
Ed

Why don't you try swapping your apartment on Craigslist...it's a great way to get to know another's neighborhood and you won't have to be in a hotel room. Just go to Craiglist/NYC apartment swaps.

i have just booked for 4 nights and 5 FULL day's starting the thursday 'after' easter..... with flights (British airways) and accomodation (3*) total came to £450! which i dodn;t think was bad at all.... when we checked the flights over the eater wknd... tended to be around £100 more.... if you can go either side of the wknd you will save a little more money - .

I live in NYC - nothing in or around NYC should be any more expensive or closed because of Easter/Good Friday/Passover. Perhaps on Easter Sunday some restaurants and shops will be closed, but if you go to an area like Chinatown you should have no problems eating.
I don't know about flights, since Easter is big in Europe, I'd expect a slight increase.
