I usually will tape the strings that the player isn't using at all, and strings that he doesn't need the open note, section by section as we record.
As any stage manager will tell you, gaff tape fixes everything. Fixes ringy headstocks, fixes loose cables, fixes unlabeled desks, fixes loud singers. Comes off clean and you know who's boss at the end of the day.
$30? That's seems kind of high.