In the case of those 6-digit salaries that Google engineers get, I admit it's not entirely unreasonable. If they really do want to own all your ideas and they're willing to pay extra for it, then why not? But know what you're agreeing to. And it's certainly not reasonable for a company paying you 5 figures to expect to own everything you think of.

It’s not just a claim on some pseudo-equivalence with respect to hourly rate. It’s a claim on the possible future earnings resulting from the activity.

Future earnings that would be reflected in the share values of the stock that Google granted to the employee that created the copyrightable material.

Not if they claim ownership on your side projects.

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.