True or False?

The following is a common sentiment from some who claim to be audiophiles.

If you hear something but can’t measure it, you only think you heard a difference.

This notion is also common among people who claim to possess an accomplished understanding of audio, especially when achieving a high level of performance for a minimal investment.

So who’s right? On the one hand we have Objectivists who claim if you can’t measure it, you can’t possibly hear it or if you do, its expectation bias and self delusion. Are these people correct? Do they get as good as a sound, or better for far less money by ignoring cables, power cords, mechanical isolation, basically any accessory that many have found to dramatically improve performance despite a lack measurements? Do those who dismiss expensive digital to analog converters as being no better than rather common digital components with decent measurements get just as high a performance level as those of us with MSB and DCS? Do people who claim it’s all about finding perfect speaker placement, do these people outperform those of us with systems that cost multiples more than what they pay (Who also pay close attention to speaker placement as well as everything else)? Or do those of us who pay attention to cables— digital, analog, and power, what we set our components on top of, how we place our speakers, acoustics, and tweaks, expensive DACs and the like, do we get better sound? Who’s right? And how do we ultimately determine sound quality?