Taking the least denominator - $50, if he spends just 5 hours a month trying to keep his server alive, active, update and making sure it's not down, responding to it if anything happens - that will cost him $200 + $15 per month to maintain his setup.
If you're about running a well maintained popular Wordpress powered blog, why go to the extend of doing it yourself when you can spend a little more, let the people who runs such services handle it. That way, you can keep doing your more productive work.
Unless, of course, he does nothing else but earns via the website, does it full-time and is happy spending his 4-hour a week on running the server.