The reason that the early Gen 1 LEAFs battery replacements cost so much is that they are an obsolete part that hasn't been manufactured since 2017. They are also a very low demand part and as the remaining NOS parts are expended, replacements will be remanufactured parts which will also be very expensive to do as they are essentially bespoke BTO parts. The universe of 2010-2013 vehicles still in service continues to decline as with the demand for battery replacements as do warranty replacements being outside the warranty guarantee. As the technology continues to improve there is little if any incentive to continue to support these obsolete early vehicles batteries except as required by law.
In 2016 and 2017, Nissan did offer a subsidized program for those that were out of warranty but did want to replace their battery. That program's funds were a one-time only limited program and has since ended.
It does look like there may be a third party solution in the works, and those early LEAF owners can look to that as a solution. Otherwise, it is probably worth cutting your losses, and moving on to another BEV.
2018 LEAF SL
Delivery April 10 2018
2014 LEAF SV
Delivery May 23 2014
50,000+ miles - all 12 bars - Same range as new - No warranty issues ever!