They already have problems getting and retaining talent.

don't forget that there are strong cooperations and they know their talents better than outsiders. They know who is how much worth.

Not really. In the german automotive industry there are no real exceptional salaries for engineers, it's pretty much regulated through IG Metall and everybody is earning the same in a +-15% range. That means these companies typically don't offer engineers awesome salaries in order to retain them, doesn't matter how good they are at their stuff. The only exception is (non-technical) management.

true, but this kind of information will eventually leak; job title and basic insider knowledge can take you quite far already