The answer is pretty obvious..... Look at the fuel consumption of an ERJ or for the matter, any regional jet-engine plane.
I fly ATRs up to 1000nm.... They don't make bucket loads of money and they are really slow when comapred to jets, but I can put to routes on them and still cover the expenses of the aircraft (including lease). Also, you should buy your regional aircrafts because they will make so much more money without that lease. This is my experience.
I have yet to try the new E-jets, but an E-175 consumes like 1,000 gallons more than an ATR-72-500, but only carries like 5-6 more passengers.