>but the existence of so many providers of free models on OpenRouter strongly suggests inference is running at a profit

I don't think it suggests a profit, but rather a _hope_ for a _future_ profit, and a commitment to a strategy that may or may not pan out. Capitalism rewards those who are early to the party and commit to their bit.

I second this blog post. I worked with Tom on a project several years ago and he's brilliant. Started doing python more frequently after that project and I found his blog to be very helpful in finding a good way to conceptualize pandas and python data structures in general.