The 737-700s are old NG technology. Buying brand new old technology airplanes that would typically last 25 years, or so, would lock you into those less efficient airplanes. The 737-9 MAX, that 61 of those 65 orders were converted to, burns less fuel than the 737-700 but has 179 seats instead of 126. 42% more seats with a lower fuel burn.

The contracted price for those 737-700s was never released. The numbers who've seen were just people's guesses.