I did some last year.  $14-20/A  I wish it had rained so it would have had a chance to work.  July and Aug were too dry to matter.

Here are some of soil-life's posts on doing this.
http://talk.newagtalk.com/forums/thread-view.asp?tid=107102&posts=7&highlight=high%20yield%20fly%20on&highlightmode=1#M758719

http://talk.newagtalk.com/forums/thread-view.asp?tid=181600&posts=4&highlight=high%20yield%20fly%20on&highlightmode=1#M1322022