Start-up's always pay low in the begining, though whether or not JetStar NZ can be called a start-up is debatable.
Virgin Blue (as it was known back then for the smart a#%es) B737 captains started on just over $113,000 base salary & now look at it. From another thread -
737 Command Salary 2002 was $113,300 plus retention of $15000 plus a 2% Bonus = $130,566
Current EBA which is about to expire has a minimum 737 Command salary of $190,889.
From personal experience I know that $250,000 is achievable with overtime/day off payments.
You really can't blame someone from signing up on a low salary with management promises that it will improve as the operation beds down & becomes profitable. Unfortunately what management do from that point on is well out side the pilot group's control.