Despite the heinous crimes, they still get basic rights. As to some of the costs, ac for example is more for the staff, and a lot of prisons don't have it. The only literature they get for free I'd a holy book. Anything else in the library was donated or purchased by the inmate or their friends and family. He will be in max so his only activity will be an hour out of his cell to walk.
As for the cost to execute, a lot of the drugs come from European companies who will now not sell to us for execution purposes and supply is dangerously low which is why we've had so many botched executions. It's not as black and white as people make it out to be.