Stand over his shoulder and watch him fight with crashes, freezes, almost daily "security updates", and observe the paranoia that a vulnerable OS brings.
Then remember
why you went the Mac route and breathe a sigh of relief.
That is fairly debatable. Before I switched to Macs, 2 years ago now, I never really had problems with any of my PCs, other than the occasional hardware failure.
My current Macbook Pro has had it's CPU fan replaced twice since I purchased it. That's actually the only machine I've had hardware failures more than once. I've never had issues (security related, crashes, freezes or anything else) with my previous PCs.
So, when my friend, who has had pretty much the same experience as me with PCs, asks me what justifies the higher price or lower specs of Macs for same priced machines, I really don't know what to tell him.
Then there's my girlfriend's PC that I constantly need to fix something on because she isn't tech savvy. On top of that, her two daughters also use that PC. It's a mess of a machine and she's actually starting to consider switching to an iMac (which would make MY life so easier).
So if I use my girlfriend's PC as an example to justify the price to my friend, he'll of course point out that it's their (my GF and her daughters) if the PC is a mess, which is absolutely true.
Thankfully, I don't feel the need to actually justify my choice to him, because to me the higher price is very much worth it. But he'll never see it, and the same can be said of many PC users.