Just kills me that Apple stop iterating the Mac Pro. Personally like the design but no processor, GPU, or connectivity updates...
Also, what you say is true about iOS devices, but the Mac is just as profitable as it was back when Apple was pushing out updates every 18-24months. Macs are languishing because Apple is letting them, not because it isn't profitable. I suspect focus is returning because professionals and power users really were leaving.
You're right that Macs now aren't less profitable than they were; rather, Apple probably gets more profit from iOS devices than Macs. Sad, but true.