[ATDrake]

A book is worth a) what you're willing to pay for it relative to b) the enjoyment or utility you expect to derive from it.

My threshold for relatively unknown-to-me fiction authors whose works I've wanted to try but am not really familiar with is around $5. It doesn't matter whether that's the "regular" price or what I can get during a discount sale, but that's pretty much my limit for something untried unless the book seems exceptionally promising and the sample is very persuasive. Also backlist works by known-to-me authors where I think it's entertaining enough, but the overall quality just isn't that great.

I'm willing to go higher for my favourite authors, well-written non-fiction from imprints whose quality I trust, and for useful reference stuff. Though of course I love it when I can get stuff from them for free or cheap, and I'll often buy something else that's higher priced if I've gotten something I like for free.

Due to Lois McMaster Bujold's basically having nearly her entire Vorkosigan Saga come free as a bonus CD with the Cryoburn hardcover, I went and bought an e-book edition of The Curse of Chalion from her other series, which I didn't really need (I own it twice over in paper in two languages), though of course it was during a coupon discount and I paid about $3 CAD for it. I'll be doing the same for the Borders of Infinity novella version from Fictionwise, which comes with the original framing story when it was in a collection, which hasn't been reprinted by Baen.