Using the same manufacturers as well known brands might not mean it’s the same product. It’s possible the ingredients are of higher quality resulting in a higher quality product. It’s also possible it’s the same thing, or the quality isn’t worth the extra price.

I remember there was a whole thing a few years ago about fake olive oil and fake grated Parmesan cheese (or what was mostly wood pulp which was allowable per legal definition). I think Kirkland was one of the real olive oil products, but the point is there were differences and some of the expensive brands were real and some were fake.