My experience selling tickets has been that people are least price-sensitive before the season starts (I have no idea why.). That's whenv I make the biggest margin.
I would bet it's just unsavvy buyers at that point.
Over the years I've seen several posts (not here, but other places) about people talking about buying tickets before they even go on sale, in that time between when the schedule is released and individual tickets actually go on sale. These people don't realize they're buying resale tickets, and just think they're paying market price, because they just went to Ticket Master and these are the only options at the moment.
On top of the regular unsavvy, then you have the worrying, long-term planners (who are also unsavvy). They think sporting event tickets function more like other markets with prices just going up over time. A lot of parents and significant others buying tickets for birthdays, anniversaries, holidays. And a lot of vacationers worrying about missing out on the one week they're in town. These people all buy early because they're worried about prices going up.
I'd bet it's these things giving you your great margins.