We’ll assume the charity isn’t a bad actor like Komen. But assuming that, it’s OK because the volunteer isn’t expecting any of her/his costs to be covered; all the money raised will go to the charity.
It’s been a couple of decades since I first heard the phrase “start a nonprofit, draw a paycheck,” and there’s definitely some of that around. I really think there need to be some minimum standards for a charity, for contributions to it to be tax-deductible, like >50% of contributed dollars going to mission-related activities, and <50% going to salaries, overhead, fundraising, and the like. 50% is still not very good, but right now I don’t think there’s any legal minimum.
But charities are required to fill Form 990 each year with the IRS, and people have websites where they’re all available, and they’re rated by how much is and isn’t going to the cause. Plus the salaries of the top officers are in the 990 too. So you can make your own call about the charity, with some context provided.
I think it all depends. If it means that a much smaller percentage of each donor’s dollar is going to mission-related activities, even if the total raised is slightly larger, I’d have a real problem with that as a donor. If a slightly smaller percentage would be going to mission, and the total raised was a lot larger, I’d have very little problem with it.