Yes 23K is not alot of money to make ends meet in AA. Yes the Islanders do leak a bit.
But........The ratio of AFS instructers who go direct to AIRNZ LINK is no where near as good as the ratio of MA or GBA pilots who make the jump. Instructers get paid better than GA 135 pilots but you will not get the required experience as quickly instructing as you would at MA or GBA which is why both GBA and MA have heaps of instructers CVs. Many from AFS.
I understand the frustration you have over pay especially given the investment we have all put into this game and if you want to stay at AFS and drive a fuel truck then go for it. However if you want to get to the airlines sacrifices have to be made in exchange for the required experience.