I'll play the mathematician!
This is the Area of each size:
6" - 28.274"
8" - 50.265"
10' - 78.54"
12" - 113.1"
But the 16" area is -
201.06" 
Pretty cool huh! Almost twice that of a 12" Dobbie!!!!!!!!!!!!!!!
Which equates down to $9.95 per square inch for the 16" compared to $10.60 per Sq inch for a 12" etc.