Trousers quality; What’s the indicator?

I am looking to get my trousers made from my local tailor, and after looking at my current trousers collection for reference, I am unable to tell the difference in the quality between them. I compared my Attolini, RLPL, PRL, Tom Ford to brands that don’t usually make high-quality tailored clothes like Paul Smith, Dior, etc. I do not see a difference in term of how they are put together. I mean… yes, my RLPL, Attolini trousers (love the buttons fly), and Tom Ford have nicer fabric, but that’s all… The only thing that Attolini, RLPL, or Tom Ford is superior to Dior, Paul Smith, or Suitsupply is the quality of the fabric and perhaps the fit. The construction of the trousers, on the other hand, cannot be differentiated.

What could be an indicator of a good pair of trousers if the fabric is not taken into consideration?