cotton of different quality between the 2 same items!

2 fitted sheets ordered: the two received, on time, packaging and 10/10 delays.
As against the two articles, even despite the packaging, are not similar: in fact one of the sheets fit the description and reviews here, but the second has nothing to do: cotton much lower quality, less weight less solid to loose stitches. The difference is seen with the naked eye but especially to the touch. I've washed before use to thinking and tighten the offending mesh cloth, but no, nothing to do: the two articles, though bought as identical, are not ... design error, lot or hidden desire reduce manufacturing costs while maintaining the same attractive price using a raw material of lower quality?
What's on, it's the end, I bought 2 and am only satisfied one ...
(Photo: Left: Quality Cotton announced right: poor quality cotton)