Sister-in-law had some in her yard... IncrediGirl was visiting one day, and when when one ran by, she picked up a small stone and beaned it on the first throw.
I'll see what she charges and will get back to you.
But seriously, one trick is to take a length of plastic pipe, cut it in half, place one end over a vole hole and cap it, then put a mouse trap under the pipe. Not always effective, but better than nothing.