Why did Sai Baba insist on taking Dakshina from Kashiram to the point of financial hardship? What was the spiritual lesson?

The Leela involving Kashiram's Dakshina was a direct method by Maharaj to address a spiritual obstacle. As explained in Chapter 0, Kashiram had become so eager for Maharaj to accept his offerings that he would feel terrible if it didn't happen, a feeling rooted in the pride of being a giver. Recognizing this pride as a hindrance to Kashiram's spiritual path, Maharaj started demanding excessive Dakshina. This was done to make Kashiram realize that he did not possess the ultimate power to give. The entire episode was orchestrated to remove his pride, and once that was accomplished, his financial prosperity was restored.