This is one of those things where you can actually say, “Size doesn’t matter.” Well, not that much anyway. ?
The biggest expense in making windows (at a factory) is not the materials. EVERY window is custom made. So every window has to have the same number of steps in setting up the jig, the same number of welds, the same number of components etc. These things do not change in any way according to the size of the window.
As far as the materials needed to make a window of 9 sq. ft or 12 sq. ft., there just isn’t that much cost difference in the glass or vinyl. We’re talking $6.00 here. When you compare that to a the cost of a window… it’s really nothing that I as a Zen owner am going to lose sleep over. There is a point where it does make a bit more difference and that’s when you get into windows over 17 sq. ft. (101 unified inches eg. 41? x 60? = 101?) That’s why we ask you for the size of your largest window and how many are that size or close to that size. BUT… even at that, if we get that wrong, it’s not a death sentence and won’t put us in the throws of bankruptcy.