Once upon a time I probably spent 15-25% of my disposable income on books. Even more as a child.
Now although I have more disposable income and books cost relatively more I spend far less. Not cheapness per se although I am a tad thrifty
$10 is a reasonable price to me for a book but if I see another book I want to read for less, well I will wait and see. $17.99 is far to much although I have been tempted. Generally a book that is selling for $17.99 give or take is available at my library far more quickly than a cheaper book. Go figure. And I am as happy with a library book as I am with one I have purchased. I don't reread often and if I wanted to I could borrow it again or purchase it at that time.
The price point thing is a new thing for me with ebooks. For paper books, I just saw a book I thought I would like and bought it if the price was in my pocket.
Helen