What you noticed between your Target vs Walmart shirts is not surprising. You are probably not getting anything BIFL from Wal-Mart. Wal-Mart gets other companies to make crap versions off the products. The food is typically a slightly smaller size per packaging. You can get a cookie pack for 15 cent less of the next grocery store over but it will be 10% less product per volume. It is the illusion of paying "less."

We had a black friday Ninja Blender from Wal-Mart which only lasted months. The one from Costco is years old and no noticable wear. Unless the sku is the same at both stores, I'd be suspicious at the quality from Wal-Mart.

And it isn't just Wal-Mart. I have bought children's clothes from Macy's vs Target and both Carters brand. The Macy's ones hold up longer: less pilling, stronger zipper, reinforced seams.