And yes, there are other factors at play. Mitchell Baker brings it up: The kind of work you do matters not only to you but also to c-level people and will be priced into the pay.
Who around here (who is also actually qualified enough, that mozilla would want them) would switch over, taking a 50% pay cut over their current pay, right now? Don't tell me you couldn't. Of course you could. Would it mean changing your life style? I am sure it would. But then again, that's a apparently cool to randomly ask of people who (I am assuming) earn a lot more than you do.
There are two reasonable options: You either come to terms with reality, or you change reality. The later means, in this particular case, enticing someone qualified (which includes a) being capable b) willing and c) in a social position to actually "apply" for the job) and to do it for less. Good luck.