Is PPC expensive?
That depends on what you call "expensive".
I've just run a 4-day trial of FaceBook Ads. It cost me £0.03 (about $0.05) per click.
It got me 711 visitors in the 4 days.
That's over 5,000 visitors a month.
In my book that makes "free traffic" just about the most expensive traffic you can get.
You'd need to spend many many hours doing any other traffic generating work to get 5,000 visitors a month.
Hours of your life that you can never get back. Gone. Forever.