I haven't started making "good money" so I'm not sure whether the percentages are correct, but on the face of it, it does sound accurate.
Hubbers can look at your hubs and you might get some earnings from their impressions. But to get clicks on the ads and purchases from your eBay and Amazon capsules, you need to be able to get people who are outside the Hubpages community. As nmdonders said, we aren't allowed to click on ads.
Also most articles that Hubbers read tend to be ones that have been recently published or have been shared. You have to keep sharing those hubs and keep bringing attention to them. This makes the revenue on them pretty short term.
The ones that have proper SEO techniques will be found by the search engines, and once you write it, you can pretty much let the search engines market the hubs for you. That is where the residual income comes in, so the more of those hubs you can write, the better. Of course, that is a lot easier said than done, at least for me.
Also while the statement may be true, it doesn't mean that internal views don't have value. I would think that search engines would consider the number of views as a determining factor on where to rank each article.