I think we're having communication difficulties, because what you just said (as a model) clearly places sales over distribution in penultimate importance, even if it stresses that distribution is a significant player -- and I not only have no problem with that, I 100% agree. The problem is, you're trying to use this model as an example of proof for why "distribution is more important than sales." And again, I have to say no, no it is not. By your own model!, all those free samples you speak of in paragraph 2 are setting the stage for future sales. But if there are no future sales -- if the free giveaways continue ad infinitum, i.e. pure, unadulterated piracy prevails, then the whole enterprise will have been for nothing! The distribution will have been a waste both of time and money, because no future profits will be reaped from it. Again, free samples are only smart business when they are followed by actual sales. A model of entirely free samples falls apart.
Which *proves* that sales matter more than distribution. Because (one more time) a distribution of one human being with $1,000,000 annual profits can work (e.g. you market yourself as a tutor for the Sultan of Brunei's sons), whereas a distribution of 1 billion people -- one-seventh the Earth's population! -- will fall apart if at the end of the year all you see from it is a bill in the amount of $1,000,000,000 for a $1 good but the profits you see are only $50,000 because a fragment of the population actually ponied up the cash to pay for it.
EDIT: So to bring this back to hentai ... say I'm a huge fan of Hellabunna. And say I try to convince Iruma Kamiri, "Look, you ought to give away free samples of your Inu series to get people acquainted with the proper channels for making future purchases of your works. Put the Inu free samples up on online stores that can be accessed internationally and charge people only for the cost of shipping and handling. Then, later, when those same people visit the site looking for your newer work, they'll already be familiar with how to order it and they'll be more inclined to purchase your works instead of torrenting them." He might be convinced by that. That would be the model you speak of, a model I agree with to a large extent.
But the thing is, you turn away from your model in some of your sentences and seem to suggest that it would be okay (even downright awesome) if Kamiri-san continued to release all of his works for free that way, as "free samples" to raise consumer awareness. That just doesn't work. If he's at all concerned about making a financial profit from his works, he can't continue to give away Inu, Rei, and all the other stand-alone works for free. He has to draw the line somewhere and say, "This, I won't release for free. This, you have to pay for." And the problem is:
1- there are people in Japan who say "F U" to that, scan his material, and distribute it through Share / Winny / etc.
2- people like us also say, "Umm, no thanks" and download it for free rather than paying for it
If Kamiri-san writes doujinshi for the love of it, he won't let this get him down; but if he's become financially dependent on it, he may say "Hell with this" and quit releasing altogether.