Pete Rose Endorsed Baseball BatThe size, and the model of the bat, as well as the condition, and year made will all dictate the vale of the bat.
Baseball bats that are the actual size, same model number, and made during the ballplayers playing days will be of higher value. A pro model bat will also be worth more than a store model bat. Store model bats typically have inch marks on the knob of the bat. Inch marks is the number on the knob (not model number) indicating the size of the bat. Examples of inch marks for a 33 inch bat include: 33, 3 or PR3 (Pete Rose 33")
The baseball bat could be dated by the center label on the bat, and I will leave a link below to help you date your bat. In general a Pete Rose endorsed store model, full size baseball bat is worth between $20.-$30. and a little league bat normally 30 inches or less will sell in the $10. price range.