I thought it was a good point to bring up. Comparing raw income doesn't mean anything -- you need to at least take cost of living into account. 75k is barely livable in SF, but quite comfortable in the Midwest, etc.
If Germans are making less but are worth more... There's interesting things going on that probably need to be taken into consideration in such a conversation.
PPP (Price Purchasing Parity) is the definition of cost of living adjustments. If you see PPP, then that's already been factored in as well as the science can.
I thought the distinction was fairly clear, but perhaps I should have emphasised it more?