I spend about $100-$150 a month on books. This includes my Audible membership.
I read mainly romances, some cozy mysteries and urban fantasy. For me reading keeps me calm and gives me an escape from real life. When I am feeling stressed, worrying or upset I can pick up my Kindle and just leave it all behind. It relaxes me and is good for my blood pressure and fast beating heart.
This is how I justify spending so much:
I've had to give up so much in past years due to my health. I can't have soda, coffee or tea or any alcohol. I can't eat anything spicy or Italian (Tomatoes and Sauces) so I haven't had a pizza in years and I can no longer eat Chocolate since 4 years ago. Most Veggies are out too and I love Salads. Even fruit except the dried kind. I can't even have a greasy cheese hamburger. *sigh*
So with all that money I save on the stuff I can't eat I buy books instead. I don't have any other hobbies so when you break it all down it isn't alot.