I'm sure Paul Roark has some experience with trying to earn a few dollars from a web site. He has certainly given away many of the best techniques for producing outstanding black and white prints. Yes, his site does request a donation, which I have done from time to time - though I'd confess I've donated far less than what his information is really worth. Does voluntary contribution actually cover a significant portion of the site's costs?
If Paul charged $10 per PDF download, I'd say it was a good value, but I wouldn't know that unless I read and tried the processes he describes first. For $100 I'd probably never read one. Monetizing the web is still in its infancy and its going to take another ten years before we settle on better models. Ask the newspaper publishers - they're still scratching their heads.
Homer