While I definitely wouldn't claim that the Google software engineer compensation package is enough to buy everyone's side projects---obviously, because some people consider theirs priceless---I suspect it's enough for a lot of engineers to be willing to sign that away (especially given that there is a process for having the company explicitly relinquish their copyright claim back to the creator).

Google pay their engineer outrageous salary.

Yes, and we’re all just temporarily embarrassed millionaires.

At Google engineer rates, that would not necessarily be an unreasonable assessment.