How many baseballs get used in a game?

Watching the World Series, I see balls get fouled out of the park, homered into the stands, tossed to fans by players after retiring and inning, or just generally inspected by the umpire and judged unacceptable. It makes you wonder just how many balls get used in the course of a game...

According to MLB, between five and six dozen are used per game (60-70 balls).

Have to have 90 on hand

The home team has to have 90 new baseballs on hand for each game. That doesn't mean they'll use them all, but they must have them, just in case.

Average life of ball is 6 pitches

This is an interesting question. I am not sure if a true average can be reached due to climate and other issues and yet here is what I found on the web through yahoo. According to Ensley, "every major league game begins with six dozen balls." He goes on to explain that the average life of a ball is six pitches. Since most major league games average between 250 and 300 pitches, that would put the ball count at about 40 or 50 balls used per game.

About 72 balls

According to the MLB: "between five and six dozen baseballs are used during each baseball game, as many as 72 balls."
Each ball costs about $3-dollars, so that works out to $216-dollars worth of balls for each baseball game.

Answer

Using an average life span of a baseball in a typical game as 6 pitches and the average number of pitches being 275 per game. The number of balls used is 46. Factoring this number out to each team in the league playing 165 games and dividing by 2 since two teams play each other each game, the number of baseballs used during a typical MLB season would about 113,850 balls per year.