With regards to the original post, new designs in amps are quite possible. Examples: Atma-Sphere (first fully balanced zero feedback OTLs), Berning (first zero hysteresis air-core transformer coupled amplifier, can be single-ended or fully balanced), class D, Nelson Pass 'first watt' amps (zero feedback class A with single gain stage)... I can go on if you like.
The same is true of preamps: Messenger (single ended direct-coupled output) Atma-Sphere (the first fully differential preamp, also all-tube with direct-coupled outputs), buffered passive systems.. again I can go on about this.
I can tell you that cost is by no means the last word. For example our preamps employ a simple circuit that has a direct-coupled output; the result is a lot cheaper than the competition that operates at the same level. OTOH if you have a well-done Dynaco PAS-3 mod, it can kill a lot of preamps costing a lot lot more! In high end audio a lot rests on the design itself, and in that on the intention of the designer (and how competent they are). This *does* mean that price may not amount to anything!
Component quality makes a difference too, as well as more arcane things like how well the circuits are grounded, quality regulation, layout, ability to survive rough shipping (that latter being quite important; I know of one popular preamp that is held together by hot-melt glue, if dropped it goes from 'sounding great' to 'fire hazard').
Intention can be huge. It makes a big difference if the designer is an audiophile (it also makes a difference if he went to school...).
Bottom line is there are many variables, cost is not the object, there are new designs that can make a difference, and you have to listen because everyone says they have the best, and that can't possibly be true- there can be only one.
Have fun :)