It won't bother me if Walmart is running a super sale on a book and I end up paying the same or a little more. Amazon - $3 is a good mark for me.
I like the $5 book price best. Love Baen for that. $10 for a NYT's best seller was a great deal. $15 doesn't bother me but it will likely be a cause for me to defer/delay a purchase. Not because I think it's somehow WRONG -- I just wouldn't pay $15 for most hard backs either.
Like everything else, price is a factor in my purchasing decisions. If Amazon were to drop their prices to $1 for ebooks, I'm sure I'd buy even more than I do now
Let's say the latest Honor Harrington book by David Weber comes out and it's $26 retail being sold for $20 "on sale" at Amazon and everywhere else. I'd probably pay $20 for the ebook because I'd want to read the book right away and I'd RATHER have the ebook than the hard back.
Lee