Well you are trying to find an equation that should have other variables in it and which we cannot count.
For example if you have set the correct value of ticket price, if your team does not perform well, the stadium wont be full.
With my second team I have the "correct price"
Previous season well performing always full.
This season underachieving (staying on same level) I never get it full.
Add to above other similar factors like the quality of the oppo, parking and other facilities of your team (for lower levels that have not maxed out) and you can have a ****ed up equation:
So dont bother at your level you are in no need of money so just fill your stadium for the 5% and the terror of the oppo :P