There isn't one set answer for that. In Steve's case, that's something that his agents negotiate with each of the publishers worldwide.Thanks.
The Suggested Retail Price always seemed misleading to me regarding books. I don't recall ever paying the SRP for a new book I purchased, but I have had to pay the SRP on books that are out of print for some reason.
Are royalties paid to authors usually based on the Suggested Retail Price, or some other number?