moish01, I was already impressed with you, but now declare you to be a tzaddik nister. You obviously know more Torah then you have let on! 🙂
Of course you are referring to the story in the 13th century where the Maharam (of Rothenburg) was captured by the Duke of Lombardy. The Jewish community collected a great deal of money to ransom him. The Maharam sent word from prison ordering that the money be returned to the donors and remained in confinement for the seven remaining years of his life.
To answer your question, yes I believe the Maharam was concerned that they may take other Jewish prisoners. (Although the Maharshal says that the Maharam was stricter on himself than he had to be. So perhaps the Maharshal is saying that the reason was the heavy financial burden on Klal Yisroel — although Tosafos says that a Godol could be redeemed at any financial cost.)