You haven't. That's the sad reality for devs living in the EU (or elsewhere but not in the States). 200k is also a bit generous, senior engineers that are specialized in <xyz> tech do earn much much more than that, anywhere from 2x to 5x. Yes, 5x that amount for an engineer. I didn't believe this myself but that's really how it is.
However, given that more and more companies are becoming more open to WFH setting, it will hopefully make the things better for the devs outside the States.
Big-data, AI, HFT ... Basically anything that has been and is a hot topic and which generates a lot of revenue. But I am clearly not thinking of an average Joe level of expertise. It requires to have all around the stack skills including the ability to grasp the big picture of the product and drive it forward.
Technical skills wise, for areas from above, you'd usually be looking at the strong background in algorithms, math & statistics, internals of operating systems, underlying hardware but mostly about the CPU at the microarchitectural level and strong expertise in at least one programming language.
However, given that more and more companies are becoming more open to WFH setting, it will hopefully make the things better for the devs outside the States.