FAANG tends to pay ~300k for senior engineers. For 400k you usually need to get lucky with stock appreciation.
Hitting 400k total comp if you have the right experience (5-10 years, good brand university or companies) is totally doable.
There's a huge amount of variance, within FAANG and elsewhere.
As a simple example, SDE III at Amazon typically pays a bit more than $300k. Principal SDE, the next rank above that, will pay well over $400k.
And don't forget that during years of steep stock appreciation, like much of the past decade, actual compensation will often be higher than that.