Soooooo I realized that commercial software is no longer onpremise (Oracle) but SaaS. :D
Anecdotally, $2,000 per user per year would be a really expensive SaaS app (right?). Not exactly apples to apples but so far I think $2,000/user/yr is a good ballpark for open source value. Note also that the blog post indicates a 50% markdown in labor value because companies pay a tax to direct employee time, so people should expect to get paid less when working self-determinedly on open source.