A lot of it is "opportunities of scale", Grace Creates. Manufacturers buy entire lots of fabric, they make thousands of any one item with very little waste.
When we were little, we still had a viable garment industry in the US, remember the ILGWU and look for the label?
https://en.wikipedia.org/wiki/Intern...rkers%27_Union
Manufacturers were not-content with our own sweatshops and labor laws and so moved the jobs to other parts of the world. Same thing with the dye processes, moved to where environmental laws weren't so strict both in terms of buildings and discharge.
Since I stopped working I really can't afford much new fabric any more, so I've been buying at the local thrift stores. I can't really go out and find the perfect fabric for a given project, so I buy in advance and I have accumulated quite the stash.
I joined the Fabric Moratorium in the challenges section this year, and in terms of new fabric I've done very well. I did buy half a yard that was immediately used in a project. I did buy about 20 yards at Walmart for a dollar a yard. And that's it for this year in terms of new fabric! Yeah... I probably do spend $20-40 a month buying fabric for around $1-2 a yard at the thrift stores. My latest project was a collection just ready to go, 1.5-3 yard cuts for $2.99 for the package, not bad for a quilt top.