Its interesting that in January the initial thread author expected that by now (March) the difficulty would be approaching 9 billion.  It seems the author used more than 30% as the ongoing difficulty increase.   No wonder he saw no ROI.

In fact just 10 weeks later difficulty has only risen about half what the author expected with a current difficulty about 4.5 billion rather than 9 billion.

Difficulty increases between 10-15% seem much more realistic in the current environment when calculating ROI.