For tubes especially it's so much more expensive for idk, a negligible change in overall audio performance. Of course I can only speak for the Xduoo TA-26 (and the Fosi Audio T3, not a good amp) and well, I do not know how good something like the Bottlehead Crack would perform (and I won't ever find out, because importing things to Europe is such a pain).

I do have heard that tube amps like the Eufonika H5 perform very nicely and I 100% trust that this is true, though I won't try it out. Sure, better capacitors, probably better circuitory too that operates at the tube's limits and such, but I highly doubt this will make a significant difference.

But all that said, reviewers and audiophiles like their beautiful words and fancy descriptions, but in reality everything is a little bit less awesome that most reviews say.