Mark McGwiresigned 8 x 10 photoA Mark McGwire signed 8 x 10 photo is worth about $60.-$120.Price will vary based on condition, and the type of authenticity that accompanies the signature. Photo composition, and how well the photo displays the signature, the type of ink used, and how it stands out in contrast to the photograph will also effect the price. Sharpie would be most preferred for a photo. Larger and more desired pictures could sell for more