As a person who is a freelancer and also employs freelancers, you're right in a way. But in another way, you have to admit it's probably not OK to just say "Hey guys, off for two weeks to write a blog post, oh and if I decide to do a a few hours of time when I feel like it, you better pay for it."

It's just not realistic. Like the guy above you said, it comes down to time and I can sympathize with that. But to imagine you always have someone on hand right there willing to pay for your hours of work is where I am like "ok, wait, hold on."

I wouldn't expect to be paid to interview. But it's still an opportunity cost.

If his time was too valuable, he always had the choice to reject the interview and save that $6000. He chose to bet $6000 for a ~70% chance of getting a $200,000 job (or whatever). Sometimes bets fail. It's frustrating, but life goes on.