It would be a lie to say that he wasn't disappointed. Killing someone would give him the memories he needed to play around with and he could even indulge the curiosity of exactly what human flesh tasted like. And what if they were to kill someone with the nightmare-memory, what would happen then? Now, that would be something he would like to see. It could certainly give him a better situation of what was happening.
And he would figure this out and then find appropriate applications to his own work.
Except there it was. Samara was meeting his bait with her own, only he wasn't going to exchange anymore. No, he was going to carefully step down this path and make sure it led to where he wanted it to go. He wasn't ready for his true ending, so he might even take her lie. Eli just wanted her to know that he knew. "And who might have given you their memories?" The most likely people would be family and they had both lost parents - two fathers and a mother between them. Although given that their fathers were Unspeakables, it had to be one of them if not both. "Benjamin? Elijah?"