it depends if it is authentic if it is than you are looking at a couple thousand
A Monte Irvin single signed baseball is worth about $40.-$60.Value is based on average prices of recently closed auctions. Prices may vary based on condition, and the type of authenticity that accompanies the signature. Signatures that have not been properly authenticated could sell at half the market value or less. Add for inscriptions. In a recent auction a Monte Irvin single signed baseball sold for $60.95. For more prices on single signed baseball see Related Links below.
Less than 50 cents.
The value may depend on which two players signed it.
$35-$85 check out some webs on the internet they will give you loads of info :)
about $50,000 - $75,000