Well this also shows their commitment to Tensorflow if they willing to pay to fab custom chips for it. Then again, in the Google scheme of things that's probably not a huge cost.

They've probably carefully modeled the energy savings over GPU/FPGA and found it to be substantial enough, even taking into account costs of design changes.

If you need enough chips it doesn't take particularly careful modelling to say that you'll beat an FPGA quite substantially in most cases.

For me this is true. GPUs on Amazon are not cheap, and if google passes the savings on from performance power consumption I'd certainly offload some work to Google cloud.

This is true - I've heard rumors that GCE has been trying hard to poach cloud consumers from other providers, this could be another stroke in that effort.

It might also give Nvidia some sorely needed worries.