The GoldCaster – The World’s Most Expensive Guitar Jhoseph King is known for building custom metal body guitars and gold-layered instruments for some of the biggest names in the music industry. King has just upped the ante, he is proud to announce that he has created The GoldCaster, the World’s first and only solid gold guitar. There have been numerous gold plate guitars built over the years but The GoldCaster is the only guitar with a solid 18ct body and custom handmade solid 18ct gold hardware.