I found the following information on author pay for different types of books published on the Liad Digest and though I would share it. The person who posted the information credited it to the authors of the Liaden books. The authors write for Baen. I don’t know if payment is similar for other publishers. Only Baen sells eArc’s .
“ It works out that the average eArc ($15) pays the authors $3, while an ebook ($6) pays $1.20, Hardcover ($25) pays $2.50, while MMPB ($7.99) pays $0.64.”
Of course total payment depends on sales volume.