Depression.

[devonin]

So a normal person may appreciate good feelings more than my hypothetical happy man, but the positive stimuli evokes the same response.

My whole point is that I disagree with this assertion of yours. You'll notice in my diagram that if you count it out, the first example, the happy stimulus is 20 -'s happier than the worst thing they have experienced, and in the second, the happy stimulus is 6 -'s happier than the worst thing they have experienced.

You seem to be claiming that in both cases (20 -s' better, and 6 -'s better) the person will react the same way, and I simply don't see how that makes any kind of sense.