It's helpful to look at old subscription prices when trying to set new subscription prices. Note that MIT is closed on Christmas Day/Eve and New Year's Day/Eve, and so we don't dance then and the subscription prices should reflect that. Also students often go away between finals and IAP and during spring break, and the student rates should probably reflect that.
Class members get their first class free, so to be sure there's a financial incentive for class members to buy a subscription, the subscription period starts the second week of class and finishes the last week of class. This exactly determines the dates of all of the subscription periods. The dates for class are determined by the PE calendar which is related to the academic calendar.
The current price for admission to a single Tuesday dance is $2 for students and $4 for non-students. For the summer of 2007 and before it was $2 and $3.50. (The increase was to include early rounds.)
For a time ending Spring 2008 there were two prices for subscriptions, with a further discount for paying extra early (the chart below lists the lower price). Sara's theory is that the only reason people don't pay early is that we fail to set the prices far enough in advance, and the dual rate meant that the only slightly discounted rate was barely worth it financially, and so she advocated to get rid of it. (The one time she had a non-student class member show up two weeks before the class started because they were unemployed and needed the extra discount.)