Even then you run into issues. Most DIY'ers use offset quilting. Most manufactures use baffled construction. When I took my Slumberjack bag apart, I descovered that the fabric did not run head to toe but three strips ran side to side. What looked like a seam holding a baffle, was actually a seam holding a baffle and a structural seam holding two peices of nylon together. So basically what we make is much more simple than what the manufactures make. Not to mention they have sewing machines that can do things that your machine can't.
But, hey its your time and sanity...
I had superhuman powers, but my therapist took them away.