What if your aim is reducing costs to the maximum and try to beat competition with that? Flying a jet on 300NM sectors doesn't make sens unless you're after prestige...but fuel prices and the volatility of the market don't give you much choice.
Bombardier claim that their Q400 can compete with narrowbody jets on 400NM sectors. Many airlines fly those distances with 737's and 320's, I have even seen some airlines flying less than 100NM sectors with those jets. Is the company image so important that you'd be willing a to pay more for your operational costs when turboprops can do the same job? Or do fares alone represent the only viable argument to passengers...Look at Flybe, they don't seem to be unhappy about their Q400's.