Hi Mike I posted my review upon my return last month (January 2018). It is on the other site: https://www.boytoy.com/forums/topic/24877-sauna-thermas-barcelona-was-amazing-tonight/?page=3
The cost is about 50-60 euros. Massage is about 30 euros. I carried about 200 euros with me, in case i wanted to play with more than 1 guy. I carried minimal things with me - just a cellphone, and one bank card. The rest was in the hotel safe. You will definitely have a lot of fun. Enjoy!