Don't forget also that these A350's are brand new aircraft direct from Airbus. That means each one of them will include Pilot Training subsidies/courses from Airbus. So in fact there's no need to charge pilots a cent for the first batch of conversions.
The sole reason for these bonds is to force pilots to remain at HKA in spite of whatever dirty moves they pull next on you. If hka was a genuine career employer they wouldn't need to resort to such trickery.