I've been a developer and I've managed screeds of developers, so I'm talking from a position of some knowledge (although others on the forum will back this up as well). On a full-time basis, $50 an hour is a pretty standard rate for a mid-level developer in the US. If you're looking fora  freelance developer, expect to pay a premium ($65 an hour is a good mean). That's for relatively common stuff - Ruby on Rails, node.js, Python, PHP (Laravel, Yii), C++, C#. Go to something arcane - weird frameworks, unusual hardware, CUDA or OpenCL software - you're going to be paying $100+ an hour.

To be brutally honest, I think his estimate as to the length of time it would take to complete this was premature. That notwithstanding, the rate he is currently "earning" is below average for the task. Comparing it to minimum wage is laughable - that specialist developers earn a lot of money goes without saying.