Once again, it's reality... The largest portion of a school operational budget is teacher's salary. You're not going to attract decent experienced teachers(especially IB trained) in one of the most expensive cities in the world without paying a premium. More international schools also mean more challenging to do recruitment so better schools make sure they offer better pay to have good retention and fill vacancies as early as possible. Recruitment now starts in November whereas a few years back, it was in the new year. I've heard that some schools offer a bonus if you resign before the end of September.