Unless I'm doing my math hugely wrong, $50/hour is a little over $100k/year. That doesn't seem particularly low, at least not in my area.
In my experience for good contract work like this the prices start around $50/hour (at least in big cities in the US), and tend towards 75-100.
I'm not saying that _this_ should cost that much, just taking a stab at the rates I usually see in the DC area.
Additionally, the contractor has to set aside sufficient profit to cover the risks involved in short-term work. Business development takes a considerable amount of time, and it can be days (or, in some cases weeks) before another contract starts. That time has to be paid for.