One great thing about this is that with Leanpub, the money you earn while your book is in-progress and selling is not an advance (i.e. a loan), it's earnings. You own your work, and you can sell it with a traditional publisher at any time.
We've had traditional publishers pick up a few Leanpub books, and attempt to get more. If you look at our bestsellers list (https://leanpub.com/bestsellers_lifetime) you can see why.
Leanpub raises the BATNA to doing a deal with a traditional publisher. Since we pay 90% minus 50 cents per copy in royalties, you earn $17.50 from a $20 ebook. The types of books that HN readers would write would do well to be priced at this price point. Authors choose the minimum and suggested price. So, if you sell 1000 copies at that price, that's $17,500; if you sell 5000 copies at that price, that's $87,500.
Because of this, lots of "niche" books that would sell fewer than 5000 copies (and not be worth it for a traditional publisher) are totally worth it to be done on Leanpub, just for the direct revenue. Plus if you consult, a book is a great business card...