I think you are misinformed. Some people read the developer agreement this way and trumpeted loudly, and it is a fair interpretation, but as I understand it Apple only retrieves the 70% they paid the developers from the developers.

See http://news.cnet.com/8301-13579_3-10205293-37.html and skip down to the "Updated 4:00 p.m." at the bottom of the article where the journalist adds the response from Apple's representative.

Are there sources where developers document being charged 100%?

That does sound much more sane, good to know.

I guess any increase in returns from this Google Voice palaver will get highlighted if more than the 70% is taken from the developer's account.