LTE there is actually pricy when you look at unlimited data
They may be seeing slower growth but that is because their market is saturated...there are no more "new" users. They must get it from other wireline customers or try to up sell current customers. NTT is the largest mobility company there, so they would be fighting with themselves. SoftBank is the Sprint of Japan and AU/KDDI isn't going to stimulate this kind of panic.
These are new sub teaser rates just like US wireline has 6-12 month teaser rates. That doesn't mean Time Warner Cable or Cox do the promos because they are competing with Verizon Wireless LTE.