Similar experience at Chelesa Men Spa. Daniel basically stops the massage 10 minutes in to discuss the tip.
I tell him that I'm always fair, and I'm a regular at CMS, but he pushes and wants to know the amount. I feel like telling him that it was going to be 60 (100%), but it just dropped to 20 because I'm not happy about negotiating. Instead I tell him that I'm not talking about it and to just finish the massage.
Never again.