Which, for someone who can establish a good relationship with a good publisher, is a perfectly reasonable position to take. Publishers are like any other service. If they provide good value, authors should use use them and otherwise not use them.
On the other, other hand, editing, etc., is a one time cost. And, as far as I can tell, <$10,000 per book.
Publishers, however, take their share per-copy. And, IIRC, the final profits are divided about 50/50 between author and publisher.
Charlie may be leaving a significant chunk of money on the table, given his popularity.
I wonder how much more work it would be to get a good relationship with a single priced editing service over a traditional publisher. Hey, maybe you could even get your agent to do that.
Maybe. On the other hand, I suspect that, precisely because he is a popular (at least by genre standards) author, he probably also gets some benefit from the publisher in terms of sales, promotion, etc. I've heard from a number of sources that one of the issues with going to a traditional publisher for a new author today is that you have all the publisher overhead while not getting much of an advance or much in the way of marketing and promotional support.
But I don't know how the relative economics work for an established author like Charlie. Empirically, most known authors seem content to stay with publishers so I'm guessing it makes economic sense for them. But I don't really know.
