Let me start by saying that I understand that the answer to my question will include a large range depending on many variables. I am not looking for these variables but I am looking for the range.

MY QUESTION
Does a club or organization keep statistics on the tow distribution (different altitudes) and quantities of each tow altitude it takes to get the private glider (in the US) if the student is ab initio (starting from no aviation experience)?

I have guesses and anecdotes from glider pilots from all sectors of the gliding community so I'm not looking for things like "...about x many..." I would really like to get real data from real students or organizations that are willing to share.

If you are an individual that has recently taken their checkride, I would like to hear your numbers as well if you are willing to share.

Example (only an example, not presented as the a good answer)
20 tows to 1,000 feet AGL
25 tows to 2,000 feet AGL
35 tows to 3,000 feet AGL
1 tow to 4,000 feet AGL

MY GOAL
Develop a cost estimate RANGE for obtaining a private pilot glider for an ab initio student. Link to a rough draft of a very preliminary ESTIMATE, mereley a starting point: http://goo.gl/NlBYmH Based on the limited data that I have collected so far, the average is likely going to be higher.

Thanks,
Jamie Shore
Soaring Club of Houston