John Elway is a former professional football quarterback. The worth or value of one of his trading cards can be determined by the condition of the card as well as supply and demand. A sports card dealer can give an appraisal to you as to how much it is worth.
With NO autograph, and in mint condition without a single flaw, that card is worth 50 cents. Autographed, it's worth about $10. If you tried to sell it on eBay with no certificate of authenticity, you'd be lucky to get half of that. Source: Huge memorabilia and card collector