There you go. You expected before listening to your brothers porta pro that it will sound different. A blind A/B testing would be way more accurate where you dont know which one youre listenning to
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Also, of course price class matters, but the higher up you go the diminishing returns drops like a nuke. For example, apple earbuds to koss portapro is a leap, porta pro to m50 is a leap, m50 to dt880/990 is starting to push it, but dt880/990 to HD600/650 or k701 is not a leap, they are technically on the same level, just different sound signature. From example the hd650 to lcd-2 or h800 or whatever other flagship you name, its way out there and I will not buy any of them. The price increase does not warrant a 10-15% increase in fidelity.
For me, I'll go MAX $500 for headphones and $200 for dac+amp. I only buy the amp+dac only to sleep better at night to be honest, nothing major. I know damn well there are better out there, but ignorance is bliss, right?