I can imagine two different reasons for the higher salaries. Companies may genuinely think higher education makes their employees that much more productive. And you see that in their hiring process.
Or the degree is something else. A marker of status. Or a signal of IQ and conscientiousness, since companies are legally barred from directly issuing IQ tests.
An observation of 2-3x higher salaries for graduates doesn't differentiate these two theories.
But rereading your comments, maybe that was never your argument. You said:
> The learning is entirely secondary. The cheating will stop when there is no longer any economic incentive to be there in the first place.
Companies might be entirely rational in offering 2-3x higher salaries to people with degrees. If that is the case, it's not just a meme. And the economic incentive will remain indefinitely. And universities and companies aren't doing anything wrong here.
Throughout your career, on the job performance matters a lot more in aggregate than your CV. Most people are hired from referrals, after all. If students value the degree over the education itself, they're cheating themselves out of all the benefits - economic and otherwise - that education can provide them throughout their career.