If we are free to use anecdotes I will base my evaluation on two friends who are copywriters and another one who's a tech writer. All of them using an Air or a normal MacBook for the work they do.
I'm curious on what your usage is as a writer for paying a premium on the Pro, care to elaborate?
P.S.: English is not my native language and I'm really trying to not sound condescending, I'm genuinely curious.
But for people who are writers and nothing else, I think the retina display was a big draw when the machine first came out.
The point I was trying to make above is that people who code, or use a pro laptop for editing or whatnot, still have to do a lot of writing as part of their job. So the keyboard on these machines matters a lot. And pro-users tend to be on their laptops all the time, which makes the ergonomic issues more important.
And it's a sad state of affairs in HN when I get downvoted for that, felt like I'm on Reddit now.