Earlier quoted context omitted.
The thing about not coming back is probably true (30% the salary?!), but yeah, not many leave in the first place.
Adding to that, is there any general reason for a German, besides money, to go to the US? So if the ones that go mostly do it for the money, they'll most likely stay gone.
I know people who emigrated to the USA decades ago, and now send their children to German colleges because those are practically tuition free for EU citizens (you need to pay rent tho). If you want to move back more early on, you can use your savings from your time in the USA to get the bulk cost of buying a house in one of the regions with good tech jobs like Munich out of the way. Then you can live a great life in Germany even with the limited German tech salaries.
Note that I'm not saying that you shouldn't go to the the USA in the first place. In fact, I'm still strongly considering it myself. But the less healthy, young, single, and childless you are, the more advantages does Germany have for you.