Maybe ask that question over at teamblind? According to a somewhat recent discussion of Sep 2018 at teamblind the TC (total compensation in one year, usually not counting any perks) should be at least $750k+ TC, source: www.teamblind.com/article/Engineering-director-at-Google-uaJEgaho

Another reference might be: www.levels.fyi/SE/Google/Facebook/Microsoft

Levels does not have L8 estimates yet, but L7 is already beyond $600k+ TC.