As already stated, Bargain editions of books are the big exception to the difference in pricing. Many times you could even buy the mass market edition of a book for more than the hardcover bargain edition in stores - especially now that many authors including Cussler go for oversized mass markets priced around $9.99.
Bargain books are overstock - usually the publisher printed too many, they were sent back as unsold and sent back to Barnes and Noble as a bargain book to move stock out. This usually happens well after the paperback has come out but it varies. Since publishers are the ones who set the e-book prices, it's unlikely you'll ever see that price lowered (at least not for a while). Barnes and Noble however, is able to move the print stock and can take a hit on the pricing.
Bargain books are first come first serve, once they are gone they won't be that price in that format again. Therefore yes, at times you will find that a bargain edition of a book is cheaper than the e-book edition. With digital editions there is no 'bargain' edition, it's an infinite amount of the same product in only one format. No need to move through stock since there technically is none.
The $9.99 you see for that is actually the same price as the oversized mass market edition in stores. It's up to you if you would rather the print version or the e-book version, but the prices with bargain editions will never match.
