If your point is that perceived pain is aggregated, you are right, of course. The above analysis is misguided, one should really look at the brain structures that make us perceive torture pain as a long-lasting unpleasant experience. A quick search suggests that the region of the brain primarily responsible for the unpleasantness of pain (as opposed to its perception) is the nociceptive area (area 24) of the Anterior cingulate cortex. I could not find, however, a reasonable way to calculate the dynamic range of the pain affect beyond the usual 10-level scale self-assessment.