A look at today's mass market paperbacks might help.
The latest NYT top 20 best-selling mass market paperback list has ten books at $7.99 and ten at $9.99 (all figures US). Are there MMPs selling at significantly less than these prices? The answer is yes - Harlequin and their competitors in the series romance market. Most of the 12 million books that Harlequin sells each month are in their over 50 romance series with prices ranging from $4.50 to $5.99. Harlequin also sells non-series books at the normal price.
The romance series books are marketed and sold like magazines: a shelf life of a month with most sales outside of bookstores. The books are also shorter than a typical MMP at 192 to 296 pages. And with standard lengths and known print runs for some 80 books each month Harlequin and other romance series publishers likely have the cheapest per unit print cost in the publishing industry.
Bantam had the short books (all but one at 100 pages) but shared nothing else with today's low cost MMP publishers of romance series. And, of course, unlike Pocket Books and publishers today, Bantam neglected to put a price on its books.
Below are a recent 500 page $9.99 MMP, a $5.99 Harlequin and a 10 cent Bantam with the price sticker the publisher eventually added.
Ace Books - March 2007
Harlequin Historical 999 - July 2010
Bantam 20 - 1940