Eternity,
Peach is a subsidiary of ANA. I believe the going rate for an A320 contract CA in that part of the world is approaching, and in some cases, exceeding 20kUSD/month. Possibly management has determined it doesn't make sense to pay the low cost pilots more than the mainline pilots. It could create havoc across the system.
If an independent low cost such as RyanAir or Air Asia started parking airplanes rather than offering more money then I would start to worry. I think Peach is more of a test case to figure out how the Japanese market responds to additional low cost carriers. Air Asia Japan didn't last long.