I'm not calling anyone out BTW.
I'm saying that a plane ride make it prohibitive for some. Those people don't even consider going. Period.
Those that live a car ride away are more likely to say they are going to go and hold on to that intent longer.
Therefore, you'll literally see way more people in the greater Philly area declare they are going and then don't make it for a number of (valid) reasons. I'm sure that happened this year too.
We had our first club meeting last night since Philly 2013 was introduced and it's obvious that the whole club is giddy excited about it. We pub-crawl Philly quite a bit so it would be really odd to not see at least half of them there. Of course, the full conference pass is probably twice as much as what you'd spend on a crawl. Add in a weekend of hotel and food and it's still an expensive weekend for most. So far, airfare has been 30% or less of the whole NHC cost.