My experience is different to the responses to your question so far. I am a very experienced BDSM passive guy who particularly enjoys CBT.
For me there are two pleasures involved. The first is the personal challenge of endurance and showing off to others what pain I can take. The second is more basic and depends on the tops skills with building up the pain. In any SM play you cannot go from 0-100 mph in one strike. It is all about a gradual build up. The top has to read the signals from the bottom and the bottom must be clear in the signals they give off both verbally and nonverbally. What I am looking to achieve is not the most pain but the flow of endorphins which results from a good build up. Go to fast and the body goes into flight and fight mode and adrenaline is not a self made drug you want. Cortisol is even worse. Why endorphins are so addictive? They are the body’s own morphine. The buzz is intense and very long lasting. The feeling of wellness fantastic.
I suppose for me I am just exploiting free very powerful self-made drugs.