Good question
Yes I was, and such variability would be possible, but in the case of the Jays it doesn't seem to matter.
Comparing apples to apples (first half of 2012 vs first half of 2013) the amount of increase is the same:
First half 2012: 1,224,816 total, 26,626 per game
First half 2013: 1,445,173 total, 31,417 per game
+ 4791 fans per game
Source:
http://www.sportsnetwork.com/merge/tsnform.aspx?c=sportsnetwork&page=mlb/teams/040/attendance.aspx?team=040