Black Mirror had an episode covering this very issue called Hang the DJ. (Spoiler alert!) Essentially a giant computer was simulating billions of human-to-human relationships using virtual (but sentient) people to see which would work, and which wouldn't, in order to make a dating app more accurate, before culling them off. I thought it was absolutely terrifying, yet most viewers overlooked the ethical issues of mass simulation of life for trivial purposes and thought it was cute(!) (I should stress that in the episode, the virtual people caught up in this are portrayed as being sentient and aware, they're not just a bundle of numbers and formulas like "people" in a game like Simcity.)
If sentience is your litmus test, how do you define it? Do you recognize partial sentience? The struggle of all life to survive and reproduce? Animals with social hierarchy, tool use, problem solving or math skills? Where is your line? You might enjoy the philosophy of Peter Singer if you extend this line of reasoning. He's a bit too radical for me however.
