I think most people see a difference between working and volunteering. (For example, I generally work harder when I volunteer than I do at my real job, at least in terms of exertion.)
I think $10 is relatively reasonable for the tournament I was running, especially because I only needed around 3 hours' worth of scorekeeping beyond what I did myself. My players were happy to do it, and I had more volunteers for scorekeeping than I needed, so I think $10 was reasonable in this case.
Regarding the $2/hour, we'll see how much turnout the CPC gets. I guess the biggest reward is an hour of early qualification time for volunteers, but obviously that's something the organizers can provide for free. If it were me, I might keep the extra qualification time, scrap the $2 altogether, and just put together a raffle for volunteers.