There is no industry standard when it comes to bonds. The bond is proportional to the amount it will cost the operator to train you and how long he considers it will take to recoup that cost.
Bonding is relatively new in these parts and I feel it will soon become the norm. It has been around general aviation and overseas for some time and has finally entered into the Australian airline scene.(Virgin & QF are both bonding their 737 crews now) New entrant into the cargo game, Trans Australian air Express, are also bonding their non rated intake pilots.
There is no problem with signing a bond, provided you can see yourself staying with the Company long enough to complete the required time without penalty.
The decision to sign up is entirely in your hand.