Most organisations never come across a problem that requires neatly clustered high-end hardware.

"[T]he IBM Telum II processors are eight cores running at 5.5GHz and with a 360MB virtual L3 cache and 2.88GB virtual L4 cache. Telum II brings a new data processing unit, I/O advancements, and other features to help accelerate AI workloads."

But if you do, if you actually have such massive data streams and low tolerance for latencies that sharding them over many machines costs a lot in overhead and throughput slows down intolerably at load peaks, then these machines are most likely a bargain. They allow you to do things very few other can do, resulting in a moat around your business and locks you in with IBM.

Or you've been around since the seventies and your software largely consists of COBOL, Fortran and assembly for this line of architectures, and it would cost you two decades of the great rewrite while all your developers do very little else, then it's also a bargain to be able to stay in business.

One where legacy businesses still use the cobol programs developed in prior decades.

I recently had to wait two quarters to launch a product because the only person who knew what some cobol accounting program did was out on leave.

This is one of the many reasons many big corporations fail to innovate. It is very hard (near impossible) to implement new systems in an environment dominated by old ones (not talking only about software and hardware here, also organizational dynamics).

One where banks, credit card networks, insurance companies, government, etc. need to process millions of transactions per second on a single mission critical box with unmatched redundancy, resilience, and security, and with a support army backing it.

The one where the chips used in those mainframes have the edge on those used in servers in some important ways - more cache, higher cache bandwidth, lower cache latency. Those developments will eventually make their way into server chips and with a bit of luck IBM (et al) will have developed something else by that time which will eventually enter mainstream.

One where no other company has pushed out a processor that can borrow cache from neighbors.

It's the decade where it all comes crashing down and you're going back to COBOL.