The 2013 Business & Commercial Aviation Operations Planning Guide shows a Legacy 650 (corporate version of a 145XR) has direct operating costs (fuel, maintenance, engine reserves) of just under $2400/hr; a Challenger 850 (corporate version of CRJ-200) is a hair over $2900/hr.

If you add crew costs, you must add not only the hourly payrates but amortized benefits/training/etc. in order to get a realistic number.

In the end, doing so is largely academic because regional carriers generally get a fixed fee for departure that covers cost + profit. Any increase in costs cuts into that profit, and mainline partners are not going to pay more than their lift contracts dictate - they'll come up with non-financial incentives (this EtD program) or simply terminate agreements due to the regional's inability to meet contractual requirements.