I own a few Zimmerli pyjamas and the quality is superior. This doesn’t prove that the F pyjamas aren’t made by LX either.
The garment given to F passengers is 100% cotton. The weave isn’t any finer than what you’d find at a discount high street store. And the tailoring isn’t so unique or high quality to suggest that there was any craftsmanship in its construction.
I struggle to believe it’s more than $15 to manufacture. Probably not more than $10 if made using immoral labor practices.