How much is a signed poster from Barack Obama?

The value varies depending what has been signed. An autographed picture might sell at $300 to $500 or more . An autopen signature on plain paper is worth far less. Authenticity is always a serious concern with Autographs. The related links should help you get a feel for the value of autographs. You also go to e-bay or similar auction sites and study the results of past sales.