Tbf, when I go to conventions, there's definitely a cost to it too lol. I'll use MFF as an example as it's my favourite convention. Plus, it helps that I help staff at MFF, but if I didn't, the attendance fee would be $100. Then you gotta have the hotel room, which with 4 people is around $300-500, and then the airfare (for me, I got my flight for $116 this year roundtrip), and then there's the dining. So, it's probably about $800-1000 by the time the convention is all said and done anyway. Then again, I do usually get a discount on the room, so I'm not counting that discount.