If there is a probation violation hold, why would he have a bond too?

This depends on the judge. The probation bond would be during the time they are litigating the probation violation.

It's hard to say what is normal because a lot of factors go into determining bond. For instance, is he from the area, is he currently working, does he have family in the area, has he failed to appear at court before? There are other factors that may indicate he would be a risk for not showing up. If you feel the amount is too high or you cannot pay it, you can always make a motion to the judge to reduce it. Make sure he is represented by an experienced criminal attorney in the area that handles probation violations.