10" and wider demand more money per board foot for a reason. They are usually in a different stack, sure sometimes a 10" wide or better board can be mixed in another stack and I have had that at Heritage Woodwrights, and they figure the price the same as the other boards not the premium price since it was not in the designated stack of wider boards. The wider boards have to come from larger trees and they are getting harder to come by since we are cutting down the forests before they get a chance to grow these days. There's no more old growth forests anymore
You guy want wide boards for the same price as the narrower ones, then glue some up or pay the price, it's that easy. I sometimes pay the price since it's worth it to me and besides the customer ends up paying for it if I figure it into the job.
You are right Ed, the lumber is shipped random length and width but it is grouped together into 10' lengths , 8' lengths etc. just as it is separated into the wider widths.