Zaroff values human life differently than most people. Without human life, he wouldn't have his ultimate prey to hunt. But that is the extent of the value that Zaroff places on human life. To Zaroff, a human isn't that much different than any other animal species that he hunts. Zaroff states that the one thing that humans possess that no other animal does is the ability to reason. Therein lies the value of humans to Zaroff. A human is a valuable target.
Zaroff doesn't value human life in the normal sense. He doesn't believe that humans should be allowed to live simply for the sake of being human. During his dinner with Rainsford, Zaroff scoffs at Rainsford's belief that human life is somehow special.
"Hunting? Great Guns, General Zaroff, what you speak of is murder."
The general laughed with entire good nature. He regarded Rainsford quizzically. "I refuse to believe that so modern and civilized a young man as you seem to be harbors romantic ideas about the value of human life."
Another good quote occurs a bit later. Rainsford questions Zaroff about how he acquires the men to hunt. Rainsford accuses Zaroff of being barbaric, which slightly angers Zaroff. Zaroff explains that he is completely civilized because he cares for his future victims. The following is his explanation.
"We'll visit my training school," smiled the general. "It's in the cellar. I have about a dozen pupils down there now. They're from the Spanish bark San Lucar that had the bad luck to go on the rocks out there. A very inferior lot, I regret to say. Poor specimens and more accustomed to the deck than to the jungle."
Notice how Zaroff refers to human life though. He never actually calls them people or humans. Zaroff calls them "pupils" and "specimens." He refers to the group as a "lot." All of those terms dehumanize the men. By using those terms, Zaroff shows that he no longer considers the men valuable, living humans. I teach several science classes, and my students dissect things. I buy high quality "specimens" in "lots" of ten. Zaroff sees human life as nothing more than a sick science experiment to be stuffed and hung on his trophy wall.