There's an interesting post by Kelsey Volkmann on the St. Louis Business Journal site that discusses two very different estimates of the per-game impact of Cardinals' playoff games.
Both estimates are probably too high but the one by the Regional Chamber and Growth Association is simply laughable because it double counts: It counts revenue spent at restaurants as an impact, but then also counts things like the additional wages paid to workers at the restaurants as a separate impact. The wages are part of the distribution of the impact, not a separate impact. This is how the multiplier effect works: take the actual effect of something, imagine a miraculous multiplication, and presto!