Make it enough that most people wouldn’t want to freely take themselves out of the rotation and take the loss, if they had the option. I’m on a 5 person team, and we rotate weekly. $500 per shift. So that’s $5000 per year. I hate on call, but I’ll take that pay. It used to be $100. At that price, I would rather never be on call and loose the $1000 year ( pre tax).

Make on call pay enough that people might want to trade shifts.

And then maybe let buy and sell their shifts.

That’s my 2 cents.