Crappy fuse material that conducts badly and thus affects the sound I can grok (not that I would pay $50 for a fuse). But I would appreciate an analysis of how the fuse's "sonic" (presumably this means acoustical/mechanical) resonance is energized, an analysis of the amount of energy we are talking about, and how that energy is transferred to the audio.
I'm thinking primarily of the mass of the fuse, and how much vibrational energy it could possibly transfer into the mass of the amp. I suspect you would need a meter with Diddly and Diddly Squat ranges, and it would fall somewhere in between. Presumably these acoustically superior fuses are composed of a sophisticated mass distribution to null out modes. I'd like to see that too.
Maybe they are just made of a lead bearing alloy, i.e. solder.