amti, that's a great idea for a silent auction! Pearl stringing around here runs $1-$2 per pearl. Potential liability concerns are damage or loss to the pearls, clasp, and any other components...but I'd say that's pretty unlikely. As far as limits go, that's really up to you. If someone comes in with a very complicated 5 strand necklace are you comfortable enough in your skill set? Or you could just limit it to one single strand of pearls. Another thought...how about a lesson on how to restring your own pearls? Maybe take a group of 5 or 6 people and teach them how to do their own!