The value of the contracts will vary depending on the historic value of the contract, and the player or team official that signed the contract. It would be difficult to put an exact value on a single contract that might be unique to that player. You would have to find similar contacts involving players of similar stature, that have sold at auction.
Check the archives of as many auction houses that sell baseball memorabilia. You could try Robert Edwards Auctions (REA), and Heritage Auctions (ha.com) to start. The Contracts can be professionally authenticated by PSA/DNA or JSA and it will sell at a higher value. If you are looking to sell the contracts the auction house will help you authenticate them, and estimate a market value.