I only buy hardcovers so my average spend is a little more, but this also serves to limit my spending since I definitely won’t go on ebay and buy like a $100 copy of an out of print hardcover. So while it may be more expensive on average it also gives me a reason to not just go crazy and buy every single book I want to read.
The Godfather has some long boring tangents about Johnny Fontaine that really ruins the flow of the novel. Also the novel version of 2001 (which was made concurrently with the film, neither is based on the other) is too literal and explains some stuff more than necessary where the movie does a perfect job of showing it through symbolism.