Not quite sure here so don't take my word on it, but I am pretty sure the third campaign will be dlc and thus wouldn't cost as much. I also heard somewhere (again iffy) if you get one, you could get the other at a reduced price
Well, the japanese version [https://www.youtube.com/watch?v=me-9kWzxKoo] of the last trailer went into pricing details: both versions will be sold for 4700 yens (40 US dollars), the second and third campaign DLCs will cost 1850 yens ($15,50) each, (so obtaining the three campaigns via DLC will cost 8400 yens/70 bucks), then the complete game (with all campaigns put into a single package) will be released at a later date with a cartridge plus doodads like an OST and an artbook for 9250 yens/78 bucks.