Operating Systems:

CentOS 7.4 was used for all benchmarks except for the TensorFlow benchmarks focused on GPU performance, which were run on Ubuntu 16.0.4

Data Normalization:

To do a price vs performance comparison on benchmarks like C-ray where lower is better, the data needs to be normalized so that higher is better.
The formula used to do this was:
Range = (max+min)
Normalized = (1 - / ((100 / Range) * Value * 0.01)) * Range

Where:
Max = the largest value in the current data set before normalizing
Min = the smallest value in the current data set before normalizing
Value = a given value in the current data set that this formula is applied to
Normalized = The normalized result of a given value in the current dataset

Hardware Specifications:

The hardware specifications for the Dell PowerEdge R230 comparison server can be found here.

Per Hour Pricing for the Dell PowerEdge R230 is based on these assumptions:

You are hosting the server yourself. In reality, if you were leasing the server from a hosting company you'd likely pay a higher rate of at least $0.36 USD p/h

GPU benchmarks:

GPU benchmarks are best performed using NVidia's CUDA Toolkit and Google TensorFlow benchmarking scripts.