Not sure I agree Fr@nk, there is a lot of investment involved in somebody joining, even those that are type-rated. There is the company induction course where many will be staying in LBA at the companies expense and will require transport from their base to LBA and back again, there are 5 days of simulator, again many of those attending the sim will require hotel and transport, and there is line training.
All of which will amount to a good proportion of the £7.5k bond.