The lower costs to Baltia to operate out of Stewart compared to JFK will relate to lower cost for the passenger. More value to the passenger. Unless you live in Brooklyn/Queens or Nassau County it could take an hour to get to JFK.
Also parking at JFK-$60 a day. Stewart or should I say New York International Airport-$10. It's really not going to be that inconvenient, especially fro Manhattan and Weschester.