Those GlassDoor salaries are cash. Stock and bonus add another 50-100%. My anecdotal experience with Vancouver is that some employers will throw you 15%, on a good year.
Microsoft pays a bit less, but also employs ~30,000 people in the area.
Yes, Amazon and Microsoft HQ are both in the Seattle area. Google has 2 locations here in Fremont and Kirkland. $200K+ for senior engineers sounds about right from people I've known who went to those companies.
Housing is getting expensive, but you can still buy a small 3br for about $400K in my neighborhood just south of Bellevue, so saving $100K does sound plausible.
A senior engineer in Seattle can do the same, and save ~100K/year.