It seems that a number of online booksellers have resorted to algorithmic auto-pricing. See, for instance, this story about an $23,698,655.93 book about flies on Amazon:

A few weeks ago a postdoc in my lab logged on to Amazon to buy the lab an extra copy of Peter Lawrence’s The Making of a Fly ”“ a classic work in developmental biology that we ”“ and most other Drosophila developmental biologists ”“ consult regularly. The book, published in 1992, is out of print. But Amazon listed 17 copies for sale: 15 used from $35.54, and 2 new from $1,730,045.91 (+$3.99 shipping).

Funny things happen when you let programs determine your book prices for you.