Again, the service isn't ready but at this point right now feedback is crucial as we near launch. We strive to be the definitive service in splitkey generation.
I don't think that sending private keys via email is a good option, especially when we know most people are using one email address and it's most likely gmail.
Just for fun I tested the pricing using various characters and I think price is fair (few bucks only) if I pick up to six characters, but it grows much higher adding just one more character.
I have to be honest and say that I honestly don't know why would I use 1splitkey when I can just generate my own vanity address for free with my computer.
Last year I did something similar, just for Luada's funeral: