Serving static pages at the rate HN can generate requires less resources than playing any game on your phone.
Now, if you downloaded an off-the-shelf MP3 search engine package and merely hosted it, it'd be different.
I also don't think that surviving a sudden upsurge in traffic is a particularly impressive feat just because it's Wordpress. If anything, it highlights how inefficient Wordpress is, which might possibly be a result of trying to be easy to set up. And a lot of the people who do use it don't realise how much worse they make it by adding plugins.
This is a showcase of the progress of such inexpensive, accessible, and miniaturized (embedded) hardware over the course of a little more than a decade - back when we needed much more bulkier and expensive PC's. Yes there are better examples of things that can fit in your pocket and do the things of yester-years N times better, but I still like seeing such raw and transparent examples. Extrapolate this by another decade, it's nice to imagine about what's coming next.