Thanks, I guess?
If you’re going to volunteer, you should expect from the get-go that you’re not going to be paid. In fact, that’s the whole point of volunteering. You’re giving up your time and effort out of the kindness of your heart. The reward for volunteering is the self-satisfaction of knowing that you’re doing something good for your community.
Whoever made this posting wanted to remind all applicants that they’re not getting paid, but they did it in a very strange manner. They actually went out of their way to inform them that they’re “not worthless, but… they’re priceless.”