The important thing to remember is that different govts have different ways of accounting for things and allowing for things in aircraft and defence acquisition, plus they could have different variants ordered. Procurements systems and govt accounting systems vary from nation to nation.I have looked up a few web sights in regard to this announcement and the basic source is quoted as Airbus. This does not mean that the deal is safe in the winding, often corrupt coarse of Indonesian politics at this stage, however if the source is correct one could assume that the price is in the right ball park. I know Ngati, an awful lot of "IFs".
The item does throw into perspective the costs of military programs and I have felt that a lot of the estimations on this site for our up coming programs have been significantly on the low side. I don't see a significant surplus being available from the $20b program
Note that the $20 billion includes $1.7 billion for infrastructure so that would suggest that the possibility exists any future infrastructure requirements related to the FAMC may be already taken into account. How I have costed the A400M is based on official French govt figures: Projet de loi de finances pour 2013 : Défense : équipement des forces (in French); Senate of France. Then I add 50% to the flyaway cost: Air Transport Capability Options Briefing to Ministers 7/11/2014,para 13, pg 3. So based on those figures you are looking at around NZ$1.8 billion.