JetBlue does seem to be consistently higher than other carriers on Las Vegas (LAS) to JFK New York. Here's a comparison for August 2019.
JetBlue Only - LAS to JFK
All Airlines Except JetBlue - LAS to JFK
Note: Information courtesy of
http://matrix.itasoftware.com/ (
Matrix - ITA Software: the product that powers Google's flight search engine). Due to Southwest's uniqueness, their fares only show on their website. But, that's irrelevant here because Southwest does not fly to JFK.
As to the reason why JetBlue consistently higher, that's anyone's guess. Airline pricing is wildly complex. It's handled by computers that do millions of calculations to maximize profits.
There are probably many different reasonable explanations as to fly JetBlue's prices on this route are higher than their competitors. Without access to proprietary information, those explanations are just guesses.
My takeaway: Given the fact that JetBlue seems to always be higher than the competition, this isn't a case of excessive demand on a single travel date. And, it's also not likely to change if you wait longer. Basically, JetBlue's prices are higher because they are able to fill their planes at those prices. If you have to fly that airline, you'll have to pay the premium.