Let us start with cables. Put on Romex, 16ga speaker wire, and $100/foot silver cable.

First, do you hear an audible difference??? In not, then the issue of quality is irrelevant!! If you DO hear a difference, then the rest is subjective as you point out.

But, if you do NOT hear a difference, you can save a lot of money!

(Of course, older people like myself may not hear a difference, while younger people may. This kind of factor along with statisitcal variation and room environment have to be taken into account in a well-run DBT.)

To say that DBT's are "useless," is, wellll, is just silly.