How much is John autograph worth today?

John is a common name, so it is not possible to determine the value of an autograph without more information. The value of an autograph can depend on a number of factors, including the person's fame, the rarity of the autograph, and the condition of the autograph. For example, an autograph of a famous person who has passed away may be more valuable than an autograph of a living person. Additionally, an autograph that is signed on a rare or valuable item, such as a first edition book, may be more valuable than an autograph that is signed on a common item, such as a postcard.