You are only counting x86 cores. For cores that can do computations you are about an order of magnitude off.
If just need a box to wrap around wrap x86 cores then this isn't it. But computationally underpowered ??? Not hardly.
The latest, greatest venue in the "core count" war is GPGPUs. (Xeon Phi cards aside but they have as much function/layout in with general GPGPU solutions as not. ).
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There are some x86 based renders that folks trot out as being blocking issues also.
Apple is clearly walking away from dual CPU processor package implementations. Given Intel's pricing it is always going to be cheaper to buy two slower packages and come out with a more cost effective core count; if core count is only primary metric.
In some areas. Net total cost is likely the same or higher. The designers made trade-offs. Fewer of a couple of things and more of GPUs. Lower assembly, inventory, and shipping costs but now Apple has to design and contract custom GPUs. That is probably at least a wash on costs.
The case , heat sink , etc. may be easy to assemble as completed components but there is also a bit of balloon squeeze there two in terms of construction complexity given the likely quality and precision standards Apple likely requires.
