Yep, to put it in perspective this kind of money in Europe is pretty much a VP/CEO level of salary for a medium size company. Or just about enough to cover ramen and rent in Silicon Valley I imagine.
Contractors in London with React (which I don't do), can make 600 EUR/day. That's well over $8k/month.
It's a great scheme, and I applaud them for it, and it's a hike up if you're non-Senior, but for about 10%-20% of engineers I know it's a pay cut for 3 months. That's OK, you get to work on something awesome. Not bad, really.