You May Be Rich!
Back in 2003, the "Complete Idiot's Guide to Submarines" came out; I remember seeing copies of it in the NEX book section, but decided not to get it -- I figured I wasn't an Idiot when it came to submarining. (I did thumb through it, however, and was amused by the chapter on "Phoning the Eng at home", having just come off my "bonus" 2nd Eng tour.)
It turns out I actually was an idiot when I didn't buy the book; it's now out of print, and the cheapest used copy readily available on the 'net is priced at $424.99. And it's just not an Amazon pricing algorithm thing; other web-based booksellers all have it in the $450+ range. So, if you have a copy hanging around at home, you have the makings for a couple of really fancy restaurant dinners for the family! (And if you see a copy in your local used bookstore, you should snag it up and eBay it.)