This is dated, but interesting. Back in the 2005-06 season, the San Diego Gulls, a minor league hockey team (ECHL), reported an average attendance of 5,841 for its regular season games. The Gulls made the post-season, and had two home playoff games. The Gulls announced attendance for these two games was 2,003 and 2,690, less than half the regular season average. What gives? Mark Ziegler provides this answer:
During the regular season, teams are allowed to announce tickets distributed, often ballooning attendance figures 40 or 50 percent above the turnstile counts. In the playoffs, the league adds a surcharge to each ticket – this year it was $1.50 – to cover postseason expenses as well as a player bonus pool. You are allowed 50 comp tickets. Anything else is up to an individual team, with the proviso that it pays $1.50 per ticket. So if a team announces 5,000 in the playoffs when 2,000 are in the house, does it pay the surcharge on 5,000 tickets? “You bet,” ECHL Commissioner Brian McKenna says. “What is announced in the playoffs is very close to the actual number in the building.”
Apparently, "tickets distributed" is a euphemism for dropping off blocks of 50 or 100 tickets to local shops, civic groups, and the like. This pumps up the announced attendance and might make the team look more popular than it really is. When you put a price on it (however unintentionally), announced attendance plummets.
Ziegler also lists league policies for announcing attendance. There's a good bit of variation across the sports.
Thanks to student Wil Kirwan for the link!