Of course, development costs a lot. They will not need to rely on Google in the future if more people donate to them regularly. Consider donating to Firefox.
Why should we have to support their over priced office space?
One, Mozilla has multiple offices across the world; see https://www.mozilla.org/en-US/contact/spaces/
Two, a large percentage (perhaps even a majority?) work remotely.
This combination lets Mozilla hire talented people wherever they are.
(Disclosure: I work for Mozilla)
You don't have to support them, but if their product provides value to you, it's worth considering
That is, it's not about less good quality of life, just less high salary possible only in places with less high level of misc. inflation.
Plus passed some level, I doubt higher salaries make good corollary with high quality of life. Not that you can't have a sane happy life with a lot of money, of course. But : - it doesn't seem to to be a requirement, see for example the case of Matthieu Ricard[2] - large salary, or more generally acquiring a social status broadly recognized as great success doesn't prevent from terrible quality of life. Arguably, even you go with Camus saying "Un geste comme le suicide se prépare dans le silence du cœur au même titre qu’une grande oeuvre", not all people in [3] committed suicide out of a situation where they felt they had good quality of life.
[1] https://venturebeat.com/2018/03/23/duolingo-to-silicon-valle... [2] https://onbeing.org/programs/matthieu-ricard-happiness-as-hu... [3] https://en.wikipedia.org/wiki/List_of_suicides_in_the_21st_c...
If SV doesn't trigger that for you, think about, say, a non-profit headquartered in Monaco, that asks for donations so that its employees can have a nice home and QoL in Monaco with salaries several multiples of your own for comparable work.
