If you're a tech writer like Sandi, you can absolutely get away with $49/copy, or even $99 or $199 per copy. They usually offer extended examples online or what-have-you to justify the $199 price, but it happens all the time.
For professional development books like this, you can't really think of it in the same terms as leisure books, like fiction, where the only benefit is having a good time. There's a benefit that goes beyond entertainment -- benefits that are monetize-able by the reader. If I read this book, and I learn something that allows me to do something in 30 minutes that previously took me an hour, then I've effectively doubled productivity. That means I'm more valuable -- and therefore, the book is more valuable. More valuable = more expensive.
Hope that helps explain why it's the price it is. That said, I'm passing too. I tend to prefer physical books for professional development, or ideally, a physical + digital combo.
Edit: Ah, found sample pages and chapter 3 at the purchase site[1]. That would be a really good link to put in this announcement.
1: http://www.informit.com/store/practical-object-oriented-desi...
Physical: It's pleasant, intuitive, and the tactile aspects change as you go through the book. Page layout and the feel of flipping through the book can be nice mnemonic devices.
Digital: I can carry a few thousand books on my pocket, put copies on all my devices, do full text searches, follow hyperlinks in the document, etc.
-- Please Note --
99 Bottles of OOP is currently available in digital form only.
This is version 0.2 beta-1, which contains about 45,000 words / 240 pages. Although it qualifies as a complete book as it stands, two chapters are pending. When they are finalized, we'll automatically email you a link to the updated book.
We heavily discount it or give it away for students and others who can't afford it. We don't ask for a postcard, just an email describing their situation.