This article is from the Neapolitan Mastiffs Breed FAQ, by firstname.lastname@example.org (Barry Reder).
Well, quite frankly, a lot. Neapolitan Mastiffs tend to be rather
expensive, for a number of reasons. They are generally able to deliver
only by Caesarean and usually need to be artificially inseminated
because of the weight of the males. All of this tends to keep their
prices rather high. Please ensure that if you find one that seems to
be a bargain price that it wasn't by virtue of their care or quality
being skimped on.