Like any new TLDs, it's a gamble.
I presume people from New York are still only using the old gTLDs and ccTLDs etc, so it may be hard to sell those for more than reg fee.
If you strongly believe the market of .nyc will grow in the future, it will be best to keep them for future profit.
I'm certain that many better .nyc domains left for hand registration than those, it might be best to check lists and decide which is best to keep.