Are Expensive Balanced Interconnects Necessary?

This is the perfect example of a discussion that offers nothing but more confusion about what a music lover should do about using balanced vs unbalanced cables. Life is too short to dive that deeply into these issues. I use balanced, and I don't take the time to look back. Honestly, my ears and mood can have such variance in how it absorbs sound on a particular moment that those minuscule differences often differ as to what really sounds best, specially based on the recording you listen to. 

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).