However one might feel about the true origins of Dan Brown's "work", he has not had to pay anything out-of-pocket for the claims against him. His publishers assumed the risk and in at least one case, the plaintiffs were required to pay all the legal costs of both sides.
Were that a book PA printed accused of being plagiarized, PA would dump the book and leave all responsibility and cost on the author, no matter what their contract said. It would cost the author more to get PA to stand up.
However, if the author successfully defended themselves and even got a monetary award, PA would probably try to take a big financial piece as well as crow that 'their' legal team is great--just like PA!
My hands hurt just typing that malarky.