Where are the Computer Ferraris and Lamborghinis?

[agami]

The hardware game has changed substantially. The few desktop/personal supercomputer OEMs (Nvidia, Cray) have been commoditised into SIs of Nvidia Tesla and Intel Xeon Phi products.

Nvidia even offers a guide for Build Your Own https://www.nvidia.com/object/tesla_build_your_own.html
Other premium integrators also have configurators https://silentpc.com/elite-pcs/personal-supercomputer
Cray's XC Series is just intel Xeons with Tesla and/or Xeon Phi cards https://www.cray.com/products/computing/xc-series

Xeon Phi seems to be dead, so Nvidia is pretty much the only game in town until someone else enters the space 
https://www.theregister.co.uk/2017/11/16/intel_kills_xeon_phi_knights_hill/
https://www.nextplatform.com/2018/07/27/end-of-the-line-for-xeon-phi-its-all-xeon-from-here/

[agami]

A Tesla GPGPU is more than a mere GPU, as you are so keen to dismiss it. Furthermore, it's something that can be purchased.
Whilst I too like the concept of CAPI, apart from a few storage, and network FPGA accelerated cards, there are no massively threaded compute offload cards for CAPI. So if one were building a supercluster, then perhaps a CAPI capable interconnect would provide some edge. The cost per activated core on the Power 9 CPU might break the budget though.

So for something that sits on top of, or beneath a desk, and can perform at or above one trillion floating point operations per second, the most cost effective and practical system will be one with an x86-64 multi-core/multi-threaded CPU + multiple Nvidia Tesla GPGPUs.

[agami]

You seem to misunderstand me, and I've even gone as far to say that I am a fan of CAPI.
I'm not talking about which one is better. I'm talking about what is available today for extremely high performance personal workstations, a.k.a personal supercomputers.

The OP was asking where are the computing equivalents of Ferraris and Lamborghinis, i.e. Supercars. I doubt he was talking about PC cases with extreme styling.
So I took it to mean highly over-engineered personal computers with extreme levels of performance. Alas, highly customised workstation OEMs like Silicon Graphics/Sgi are gone. Even Apple has given up on the extreme gigaflops marketing common during its PowerPC G5 era. In a highly commoditised market, there are no Ferrari and Lamborghini equivalents; Just kits.

The biggest problem with Power9 is IBM. A company that is good at spending money on R&D, but lousy when it comes to executing in the marketplace. Power9 architecture is awesome, but all that awesomeness means nothing since it will never be in a practical desktop computer.