At a regional?

For small t-props, it can be 2 crews per plane, plus some reserves.

I would think at most jet regionals it would be typically 4-6 crews per plane.

10 crews/per plane is way too high. Each plane needs two crews per day, so that would mean each pilot only works 20% of the time (maybe a little more after you take out reserves). Say 25%...that's 8 days per month, or 22 days off each month. Not too many folks have a deal like that in regional-land.