The job I had before the one I have now, I was on call 24/7 covering a 4 state area. It was only for onsite breakfix, and I worked MAYBE 3 hours average a month (not counting drive time) and it was salary. It was awesome. The only real catch was I just needed to be available at any moment to go somewhere. Once I drove 10 hours, was on site working 15 minutes, then drove 10 hours back (and was paid $1k in mileage).
For the last 3 years or so different company and I have on call 1 week out of every 4 covering equipment for about 250,000 users around the globe. It has gotten better in that in the last 8 months they have added an overseas crew that takes over at 8pm to 8am. Before that there were times where we'd never be off the phone with production issues or doing disaster recovery testing an entire weekend. It's salary so obviously any extra hours I don't see anything for, but I was very aware of how their on calls went prior to taking the job (I was a consultant for them for a couple years) and negotiated my salary based on that knowledge. They are looking at adding a couple US people so that would move it to every 6 weeks, but even though we sorely need the extra people just for the day to day workload that has gotten out of hand, I doubt it will happen.