Having worked as an indie dev for a decade and a manager of 150+ developers for a decade, I find this comment misguided. Here's "how it works out" for me.
I wrote code as fast on an Apple //c as on this late-2010 MacBook Pro 17". I'd argue faster, as context switching to something unproductive was actually a chore. For writing, Appleworks 2 on the //c was, if anything, more efficient than the latest MS Word, for the same reasons some hardcore devs prefer EMACS over Visual Studio.
In my experience, the single most meaningful programming productivity boost in the past 25 years is a second screen.
Running PageMaker on an SE/30 with an external Radius Pivot, for example, ran productivity circles around working the built-in screen alone.
But before second screens, devs managed to get by. In the Apple II coding days, an Imagewriter printout of code thus far taped to the wall behind the monitor served as the "second" screen, and physical books lying open around the desk served as reference tools. In many ways, I'd argue the simplicity and thoughtfulness of that approach was more efficient. It's as though the mind can keep separate threads for each type and physical location of media.
For horsepower, as the rest of the comments here point out, a team does want a source code and build system that screams, but each developer workstation could arguably be a text terminal provided it can handle a few windows.
The psychology of latest toys contributing to job satisfaction contributing to productivity is a separate argument. I have found giving dev groups machines tuned for LAN parties (latest graphics, high GHz CPUs) more relevant to productivity than providing machines tuned for compiling (striped raptor HDs, quad xeons).