There are over 100 volunteers for Offkai. Let's call it an even 100. Let's say they work eight hours a day for the three days, or twenty-four hours, and Cali wage laws says they get $20/hour. That's $48,000. They're probably working a lot longer than that each day, and besides the day of the con, they need to do is testing beforehand, set up the con and breakdown and cleanup after (let's say twenty staff for another eight hours each the day before and after, and that's another $6,400). Then you've got administration, HR, all that wonderful stuff, that's going to drive up our really conservative estimate of $54,400. I'm probably severely underestimating a few things here, but this is just a quick ballpark estimate. And all of this needs to be spread out over every ticket sold.
I agree they should go with professional staff, but you can see why they tried to stay with volunteers when you see how much extra expense was added.