One can argue Jet Blue would be even more successful had it acquired the 737NG at the A320 s offered price.
Acquisition costs are often determinant in fleet decisions & ultimately, it often comes down to which manufacturer offers the steepest discount.
EasyJet is facing a similar choice: they’ve publicly acknowledged that the 737NG is more efficient but Airbus is offering a deal which more than offset the higher A320 operating costs.
Boeing has announced yesterday they would not lower their price.
It follows that EsayJet could purchase the A319 even though the 737NG is more efficient.