I agree that developers in France are rather underpaid, but you're comparing apples to oranges.
A lower French salary comes with a number of valuable benefits which makes the take-home pay difference much smaller than what you're saying : https://news.ycombinator.com/item?id=13412599
A lower French salary comes with a number of valuable benefits which makes the take-home pay difference much smaller than what you're saying : https://news.ycombinator.com/item?id=13412599