Can you detail the specific financial transaction that caused surprise during the visit of the two men from Goa?

Yes, the surprising financial interaction is a key event in the story from Chapter 36. When two gentlemen from Goa came to see Sai Baba, Baba asked for a Dakshina (offering) from only one of them, requesting a specific amount of fifteen rupees. That person gladly gave it. The second gentleman was not asked for anything, but when he offered thirty-five rupees on his own, Sai Baba flatly rejected it. This selective acceptance and rejection of offerings was so puzzling that it prompted Madhavrao, who was also there, to ask Sai for an explanation.