Remember that there's a vast difference between "net" and "list." "Net" means that the royalty is applied
after the costs of the publisher are deducted from the price. Let's look at two scenarios:
Cerridwen says they pay 40% of net. Let's take a novel that costs $4.99 on their site and say that website maintenance for that novel's page is $.50 per book, cover art is $.50, advertising is another $.30, payroll/salary for the owners and freelance editors is $.50, equipment rental for computers and such is another $.25 per book. All of these costs are perfectly reasonable costs of doing business for the publisher and the contract states that each author agrees to pay them. What does that leave? The "net" price of the book is $2.94, of which the author receives 40%, or $1.18 per sale. Now, that's not all that bad---provided the author is fairly clear on what constitutes the fees/costs withdrawn from the list price. I wouldn't sign any net contract unless I either had a conversation with the publisher about that, or limited the costs to a fixed percentage of the list price, because let's face it . . . almost ANYTHING can be deemed to be a "cost of doing business." How many of us deduct on our taxes for dining out with clients, attending conferences, hotel, airfare, etc.? How about late fees when paying bills or high interest rates on credit cards? All "costs of doing business" if a publisher isn't reputable and chooses to include them. What can happen is that instead of a $2.94 net price, it's a $.94 net price, of which the author receives half.
That's not to say that Cerridwen isn't completely reputable, because they are and their costs strictly relate to the costs to produce THAT ONE book--from what their authors have related to me. But understanding how "net" works is valuable to an author. You always have to think on your toes when signing your name to a long document.
On the other hand, the 8% paid by larger commercial publishers is based on LIST price, or the price on the book's cover. So, a $6.99 book will give the author $.56 per sale. No deductions, no changes.
But $40K to $50K per book isn't completely realistic, either. Most romance novels work out to be from $12K to $18K per title, depending on the subgenre and the popularity of the author.
I know epub authors who make excellent money. I know print pub authors who make so-so money, and vice-versa. They're two halves of a whole, so choosing between them isn't merely an issue of who pays more. A good commercial print publisher and a good commercial epublisher wind up paying about the same in reality. The smaller epubs are similar to a small print press. They don't have as much exposure to the public, so while they pay okay royalties, the number of sales aren't high.
Just remember to always think in terms of "net" versus "list" when you're considering numbers.