A smaller aeroplane is always more expensive in a CASK basis, as the costs dont decrease in proportion to the reduction in seating capacity, the 78 seat 170 has less than half the seating capacity than a 737-800, yet costs did not decrease by half, fuel burn didnt, salaries didnt (despite what some think!), financing cost didnt.
Conversly the 777-300 is cheaper than the 737 to run on a CASK basis.
Where the cost savings come in is that per block sector the Ejets are cheaper to run than the 737 which in turn are cheaper to run than the 777.
So if the sector that the ejet is scheduled on has booking of less than or equal to the seating capacity of the ejet (170 or 190) then it is cheaper to run an E Jet.
Equally if the Ejet allows you to operate on a citypair that you wouldnt otherwise be able to run on (Albury - Sydney for example) then the Ejet is infinately less expensive to run than the 737 (assuming your fares actually turn you a profit)
The Ejet appears to have been extremely popular with the punters and crew, and I reckon it will do the business for
VB.
It is a good option as compared to the 146, the F100 and the 717.