Wow, still no answers to the OP?
You're not getting much help, OP, are you? A number of "meh?" and another bunch of "whatever it takes...."
So, I'll start by mentioning an implied cost / benefit the Jacks do in showing the weight saving by filling with very expensive 900FP down instead of 800FP stuff. They show it for a winter quilt and then for a summer quilt. Obviously the more down the quilt has the more down can be saved. The % reduction in down weight is the same between quilts, but for the summer quilt which started with just 4oz, all that is to be saved is 1/2 oz. The shell has the same weight.
Now to some, the 'spensive stuff is especially a bargain. Because they're not swapping much, it doesn't cost much. To others, the weight saving of 3 US quarters isn't worth the expense, but they might feel differently about saving 2oz on a fall or summer quilt.
As a bike camper, I can justify spending seriously to save the space that can come with saving the weight. (As though at my speed, the added wind drag would be noticeable.) But serious $ to save a couple of cubic inches? Better to learn how to pack less air. Or lose 10lb of un-needed body weight, accomplished by eating 5lb of NJ tomatoes (@$0.50lb) per day for the last three weeks. (No lie. They all go in a blender.)