I once saw a documentary on Walmart and it showed how Walmart gets their items to sell. They go to the supplier and say "I will carry your stuff but I will only pay X dollars for it". Maybe the fabric suppliers couldn't offer the fabric at the price Walmart needed to pay. With shipping costs (because of gas prices) skyrocketing suppliers have to pass the increases on to the buyers.
I remember in the 70's when we had oil shortages it became very hard to buy double knit fabrics and if you found them they were very expensive.
Just a theory!