I honestly do base a number of my purchases on the cost of the book to page count, but its quite a bit more nuanced than that. If it's a brand new release from an author whose previous work I've enjoyed, I'm likely to pick it up, but if the price is $26USD on release, and that book isn't at least 350 pages, I'm definitely not buying it on release and going to wait a good little while until it hits the $15 or less price point.

If the book is under 200 pages, I'm almost never going to pay over $15 for it unless it's an author I really, really enjoy, or a topic that is especially interesting to me. I get that page count is in no way a metric for quality or likeability, but it's generally a reasonable metric for value. I'm also inclined to believe if a book is well liked &/or popular, it'll be fairly easy to borrow or find a used copy at a reasonable price, so even then, it's more a question of personal patience more than value.