dagnabbit,

There's plenty of cab's that will take you and it's a fixed price normally too. $65 + toll's from memory. I pre-booked the last time I went, there's plenty of companies out there if you do an internet search. I used New York Top Limo's, they were excellent. Our flight landed an hour early and they'd checked and arrived an hour earlier to pick us up and the return was bang on time. We had a stretched limo but they do all sizes of taxi's to suit your needs.

Darren

You might try a shuttle service (shared van) like Supershuttle- they go to all the midtown Manhattan hotels. Depending on how many are traveling it might be cheaper.
http://www.supershuttle.com/ they are at every major US airport. You will find them outside baggage claim.

A cab to Manhattan will be around $60 total.
http://www.nyc.gov/html/tlc/html/passenger/taxicab_rate.shtml

21:30 + 1hr (one hopes!) to get luggage and clear customs/immigration means you will be looking for ground transpo ~ 10:30pm. That's a little on the late side to mess around with the "train-from-the-plane"
http://www.panynj.gov/airports/jfk-airtrain.html

Supershuttle may offer some better prices, especially if you book on-line and realize that others will be traveling from JFK (perhaps your flight) to TimesSq hotels, so relatively few stops. www.supershuttle.com

Taxi will be most expensive, but very convenient and very little ground congestion that late in the evening.

People do Uber from JFK airport, but one has to know "the tricks" a bit.
http://lifehacker.com/the-uber-airport-rules-for-11-major-cities-in-the-u-s-1743405933

Whichever you choose it will be less expensive than our ride from Dover to Windsor last summer!