It seems contradictory for a desireless saint to ask for money. How is Sai Baba's act of requesting Dakshina explained?

This very doubt is addressed in the teachings. Chapter 14 poses the question directly: "Why does a saint need money?" The text clarifies that for a being like Sai, there is no difference in value between pebbles and diamonds or copper coins and gold coins. The act of asking for Dakshina was not driven by material desire, as He is described as "completely fulfilled." Instead, the practice served a higher spiritual purpose, primarily to instill humility in his followers and test their faith and detachment. The act was a tool for spiritual instruction, not personal enrichment.