No standardization necessary. At least I don't think so. It won't be a perfect measurement because, as someone already pointed out, a golfer who finishes second in every tournament will almost definitely win in this stat but may not be the best player.
What I think happens is that the higher purses are for the most prestigious events which brings out the best fields. So, this measurement kind of manages itself. Also, it might be better than a scoring avg. measurement because it is measuring golfers against others in the same field playing the same courses. The kind of things that would mess it up would be someone like Fred Funk skipping the British Open to play the PGA event and perhaps winning it. He should be punished for that as opposed to rewarded but, as I said, it won't be perfect. Just interesting.