The expensive part of making books is not the paper. My wife is an independent author and between editing, typesetting, cover design, etc. she spent about $1500 to publish each of her books.
While she could price her books at $1, that would present her with a few problems.
Firstly, people often value things based on what they've paid for them, so pricing your book too low makes people assume it is of poor quality.
Secondly, having positive reviews is extremely important for indie authors because the Almighty Algorithm will reward you or punish you based on the book's rating. Other indie authors she has talked to have seen a noticable decline in their book's rating after Amazon put it on sale and a bunch of people who might not have otherwise read it started buying copies. If you've ever worked retail or food service, you probably know that bargain hunters are often the people who are least reasonable and hardest to please. If the book is too cheap, you may attract an audience that harms its reputation.
Finally, trying to sell 2000+ copies of a book is pretty daunting for small authors and that's about what it would take to break even at $1 per copy.
Could big publishers and well known authors sell books for a buck? Probably. But for the majority of authors who aren't making their living by writing and only sell a few hundred copies ever, that's not really realistic.
I can't think of a recent time where I've seen an eBook that cost more than the paperback but I haven't been looking specifically. In my experience, the eBook is usually a buck or two cheaper than the print version.
I'm open to being wrong about this.