It’s a noble gesture (usually) for people to donate for raising money for worthwhile causes. The musicians donating their custom Les Paul Guitars (“art pieces’) to help support the Save The Music Foundation is such a one.

Chris Stapleton, Joe Perry, The Roots Contribute Guitars to Save the Music Auction

However, the prices obtained at such charity auctions often do not square with the reality of the marketplace. People are not just bidding on a rare, desirable artifact; they’re making a donation. A custom guitar may sell for $5,000.00 in a Sotheby’s or Heritage auction, but for charity, who knows. It may sell for $50,000.00 or $100,000.00. The point is these charity auctions don’t reflect the Fair Market Value of the items. If you are trying to guesstimate the potential of your item, using these kinds of charity auctions as your guide are bound to bring disappointment.