Re: Value for money?
It is good value. The cost per core is not really important, it's the interconnect (Tofu) that makes using those cores in big science applications fast.
With that, the peak:average performance ratio across a range of application types is close to 1:1. With just a large number of ordinary computers on an Ethernet, this ratio would be much, much lower for most tasks.
Tofu is completely mind bending (6 dimensional hypertoroid mixed up with a 4 dimensional hypercube), and they build it into the CPUs for the full effect of ultra - low latencies. A lot of other machines use infiniband, I think using PCIe NICs, which is fast but I don't think it's as good as Tofu.
The predecessor machine, K, was notable in this regard, meaning that it's benchmark figures were very good and very translatable into application performance.