Answer:
It highly depends on the player who has signed it.Obviously this is due to how well or bad he has played. More specifically, if the player that has signed the baseball is currently still playing it will not be worth as much even if it is a big time player.This is because he is still signing baseballs, cards etc. Now this changes once the player has retired and much later passed away because no more baseballs or anything else will be signed and the number of signed baseballs decreases from that particular player. This increases its scarcity and eventually becomes rare enough to be worth some serious dough! Hope this helps..Do you mind mentioning who signed a baseball for you? I could probably give a more specific answer opf how much it is worth.