That was a great explanation, and it helped me understand it better. However I was confused by Coopers graph because he suggested a graph of only sales charges over time, but it sounds like he described the graph for Class A as "Average Sales Fees%" over time, and a graph of Class B shares as "Average Fees$(Sales+AnualFees)" over time.
If we are plotting "Average Fees %" over time, then the graph of Class A shares would start at 5.75% and decline at a fast rate. Class B shares would also start at 5.75% as well but decline at a slower rate over time. The average rate of Class A will always be less than Class B shares. The only way these lines would intersect each other over time is if you kept contributing large sums to the Class A shares at 5.75%. In either case, over time, Class A shares will approach the Class A Fee% and Class B will approach the Class B%. However, Class B shares will eventually convert into class A and approach Class A%. But Class A will always be a lower average % over time, (assuming no more Class A contributions).
If you plot "Total Fees as $" over time, Class A shares start high(assuming a large up front contribution) and go up over time at a small rate because of the small annual fees. Class B shares start low(assuming a small up front contribution) but go up at a higer rate. Assuming Class B contributes the same amount over time as the Class A shares, at some point in time (~7-12 years) the lines cross. Your total cost will eventually be more in the Class B shares as the Class B contributions approach the Class A contributions.
Ultimately there is an optimum strategy for each of us based on our contribution plans.