I think you have to take in to consideration all the hands that cotton goes thru before it gets the the LQS>
1. Farmers
2. Pickers
3. Clean and spin into thread
4. Made in to fabric
5. Designers
5. Dyed and/ printed
6. Shipped to distributer and LQS
Some of these operations may be done at the same plant, but it still requires different machinery. Each of these operations has overhead, and if the goods have to be transported to another facility that is another cost.
I would be better if we had an accurate rate for each of these steps, but it sure goes thru a lot of hands before we see it. I would like fabric to be less expensive but it sounds like it is relatively cheap in the US. Maybe we need to count our blessings.