Back to the issue.
Is it Jetstar or is it:
1. Over 100yen to the dollar
2. Japanese package rip-offs - over inflated accom costs, Japanese owned tour operators and agents in Cairns, Japanese owned "shopping" tours in Cairns.
Perhaps the humble Japanese tourist is waking up to these rip-offs and going elsewhere!
As for the QF/J* debate, remember that QF has given poor service to the Japanese market for years. Old equipment (747 classics) and the failure of the all economy Australian Airlines has seen this market in decline for years.
Can J* turn it around? Unlikely!