They work in a market alongside people whose compensation is entirely derived from intellectual property law. Their wages are driven up by compensation from those firms.
Which is true, though that gets to your use of "a lot" in the original.
To claim that content IP licensing pays for some programmers salaries is straightforward. To extend that to argue that salaries of all programmers are significantly higher needs numbers; it's not at all an obvious corrollary.
I don't directly profit from software IPR (I don't sell shrink-wrap). If software IP was indefensible, I think I'd lose more than 40% of my market value.
To claim that content IP licensing pays for some programmers salaries is straightforward. To extend that to argue that salaries of all programmers are significantly higher needs numbers; it's not at all an obvious corrollary.