While working at Google I worked with many many amazing H1B (and other kinds) visa holders. I did 3 interviews a week, sat on hiring committees (reading 10-15 packets a week) and had a pretty good gauge of what we could find.
There was just no way I could see that we could replace these people with Americans. And they got paid top dollar and had the same wlb as everyone else (you could not generally tell what someone’s status was).