Are Expensive Balanced Interconnects Necessary?

I’m using XLR’s from my DAC to my integrated because it sounds better and they and they cost the same as the RCA’s.

I would certainly think it is system dependent. Based on my limited experience.

In a well-designed system, balanced interconnects are not necessary.

"Clearly"? Not so much (or in reality, not at all).

Balanced interconnects work best with differentially balanced components.  Check to see if your stuff is.