The 737 rating I can swallow, but a fATPL? One would have to question the veracity of your statement considering 70% of fresh faced students never realise a job in the right hand seat of an airliner. Apart from that it's quite simple isn't it, the OP has three options.
1. Call Flybe asking what he/she is getting for that type of bond and WHY is it that high for already type rated pilots.
2. Don't join.
3. Join and hope he/she doesn't have to leave within the bond period.
And yes I agree with you, reversethrust and everyone else, it is a disgrace to bond for that amount for already type rated pilots but there maybe a legitimate reason why, even if we're struggling to think of one.