It's not really clear to me that number is correct; looking on the internet I also see other (much lower) numbers, as well as mentions that ~25% goes to overhead in the form of agents and such. I can't really find a good source on what the yearly net income of a WGA writer really is.

But the strike is really about increasing the minimum wage, not the average. The "average wage" isn't really a good metric in the first place.