Aka the ones who don't think you're nuts ;)
For me, I'd say it's about a third. Certain really good recordings help out with that.
I've sold M11s to a few friends, also convinced a few to get M9s. These people are on student budgets like me, but usually much less.
Sold 3 M11s, convinced 5 M9s (MEelec, you're awesome for budget IEMs), almost convinced a Beyer T50p (woot), convinced 2 to put aside ~$70 budgets. Hopefully future girlfriend to be likes my AD700s. She thinks they're purple and cuddly.
My housemates tell me i'm foolish to spend good money on audio but they always want the Monitor Audio Speakers to come out for any house party's...
Actually a few other friends have bought earphones off me as well, (meeM6, Beyer dtx60, Senn cx55) and they seem to like them.
I have actually converted and trained a number of my friends to appreciate and enjoy a quality system. 2 of which now own old stereo hifi systems of mine when I have upgraded (and sold to them very cheaply, love to keep it in the family and I can still enjoy my gear even if it lives elsewhere).
Still having trouble finding a partner who doesn't think I'm totally crazy when it comes to audio, they might love hearing the home cinema in a movie, but truely appreciate and feel the same satissfaction as myself....yeh hasn't happend yet.
Porta-pro is not that bad really. Most people I know think portapros are ugly and apple stock headphones are the way to go. I have a couple of buddies who seem to be really into music but me trying to promote at least solid headphones to them is like bashing my head against a brick wall. Those are not the worst kind really. The worst kind are people who pay 200-300 bucks for headsets, see me wearing my hd25s and look at me indulgently like I'm 8 and done something really wrong then hand me over their purchase and say - here buddy, listen to some real sound. So basically there's no one I know in real life who is at least reasonable about the sound quality.