hey sonar, i'm gay and have seen a lot of dicks in my time...i think you just came across a group of big guys who happened to hang out with each other...i'll explain
based on my EXTENSIVE experience, the average is probably around 6 inches, but were talking the population in general...get together a group of cocky, confident guys and they're probably cocky and confident for a reason. Kong is right, most guys with big dicks know it and like to show them off. You happened to stumble on a group of them. Also my experience is that healthy, confident, athletic guys tend to have bigger dicks - not necessarily HUGE, but bigger in general
growing up i was on the swim team and have never seen such a concentration of big dicks in my life...in fact, when i started screwing around with guys i was startled to find out how many average-sized dicks were out there. These guys spoiled me for the rest of my life. On the high school team i knew at least 5 kids that were 10 inches or bigger, and one of them was easily 12. No joke. And about 10 other guys who were big enough to compete with your friends at that party. When i got to college there was one guy with a possible 10 incher, and about 8 other guys that were definately way bigger than average.
Another thing i've noticed is that big-dicked guys, staight or gay, gravitate towards one another. The gay thing is obvious, but with staight guys I think it's that they have similar attitudes, and none of them are a threat to each other. I knew these four guys at a restaurant i worked at, and they were all close to 8 or bigger. They weren't like four best-friends, but they all got along really well. The other guys at work were either jealous or completely in awe of these studs because they had it so easy with the girls.
I remember this one bartender, who was good-looking, great body and had a really smooth game. He put a lot of effort into getting a girl, and got his fair share of pussy. But he was always one-upped by this kid who was 19 and scrawny. This kid always got more girls, got hotter girls and ALWAYS had them coming back for more. And it drove the bartender nuts...what he didn't know was that this scrawny kid had a massively thick 8-incher. And the guys the weren't jealous of the scrawny kid were clingy with him because he was always so good with the ladies. So when he would go out, he would go out with the guys who were also hung because they weren't jealous and they weren't clingy. Makes sense right? Just my observation.