For anyone else who had trouble parsing the article, here's a TL;DR:
1. Why buy fancy top-of-the-line hardware when something cheap and utilitarian will do just fine?
2. The author's figure is made up. He takes an estimate of total spending and then assumes 70% of it was wasted. Based on unsubstantiated personal anecdote. But there's a page-long rant about cookware written in cringe-worthy style.
My take:
I'm sympathetic with (1). But I also know some people in K-12 IT. They're professionals with some accounting education who know how to perform a reasonable cost-benefit analysis.
Sometimes money gets wasted on expensive toys.
But sometimes it's less expensive to stick with Macs or Windows machines than retrain hundreds of teachers on Chrome OS or whatever. Sometimes there's bundling and the 30% or 70% that never gets used represented a 0% additional cost to the school. And sometimes people are just stupid.