[andrewflnr]

Obviously identifying key people is hard, or everyone would get it right. Most important things are like that.

(I don't think it's quite as hard as you're making it out, though. Who are the people you go to first with questions about how stuff works?)

Maybe we have a mismatch on what "appropriate" pay means. If the expected cost of losing someone is less than what you're paying them, maybe you're paying them more than what's appropriate. But it does sound a bit like you're falling into the same trap as GP in assuming you have to pay everyone the same rate; I could be misreading you.