I just checked Delta for November and found that they only fly JFK to SXM, non-stop, on Mondays and Wednesdays.

According to the Delta site, a non-stop is offered every day but Tuesday in November from JFK.

I plugged in random dates for Nov. 2016 and saw fares starting in the mid-$400 range and up to $900 for non-stops from JFK. Fares changed drastically depending on the day of the week with Saturday being the highest.