It's actually not a case of fearing there are people who are difficult to deal with, I have absolutly no doubt you've experienced people who are stuck in their ways have as many hidden costs as the junior. I've taken over from older devs who don't use version control, nor a dev environment, refuse to use frameworks or follow coding standards. Should we honestly believe they don't have hidden costs? Would you really rather deal with them than train a kid?

Either way, I'm only trying to counter the "old is good". I fully accept there are amazing older IT workers, just not that older is always better.