Some smart authors
have people helping them get the books done for e-publishing, and that does cut down on mistakes. It might not get rid of all of them, but you should have a readable book. Not even paper books are without mistakes, as I found several that went through all the proofing/gallery work, that a regular published book goes through before printing.
Starrigger is right that the rtf's that he sent in to the publishers was as correct as they could be, I know, as I helped proofread them for him. Proofing is not easy to do and without the actual book and the rtf before me, I would not have been able to do so. Then he went through them also, I believe. They all had to be a certain type of font, a certain spacing, rules upon rules to let their 'converters' do the work when it was done. Some rules even I will say are silly, but they had to be that way.
Needless to say, in the formats that were converted from the retailers, mistakes crept in, or I might have missed something, Starrigger might have missed something else, but the books you get from F.W. or Baen, Mobi-P, or where ever you get them, are going to be the best we could do following their rules.
Word by word, line by line, sentence by sentence, break by break, you try sitting at your computer for 12-14 hours a day to proofread and fix an rtf, lets see how well you do... will you try it?