"keep a cron job running" sounds like it you're running the cron job by hand.
>Even the top 100 sites are only at 80% https by default, and they do it for a living!
That's entirely separate from your "simple, static site" example and yes, rolling any sort of large change out to a big site is a big deal, and if there isn't business motivation to do it it likely wont happen. Google is providing everyone a business motivation by threatening to point out to users that insecure sites are insecure.