Here's the thing: I think salary alone is a better indicator than salary adjusted by cost of living.

The reason is that there is also quality of life, which is hard to measure. I think that in the absence of a dedicated measure for quality of life, rent levels are a relatively reasonable proxy, and those are one of the biggest factors in the cost of living.

So, as indicators go Salary&Cost of Living&Quality of Living > Salary alone > Salary&Cost of Living.

(Obviously this logic also doesn't necessarily hold across continents, or even in a market as fragmented as Europe, because people rarely move between different countries in Europe, whereas people move between states all the time in the US.)