Marlowe
A common misconception there. I have seen data which indicates that whilst the E170 does indeed burn around 20% less fuel than an RJ85, don't forget that the RJ85 is a lot cheaper to purchase or lease and in my simple operating cost model I think there is a signficant economic benefit in favour of the RJ85. And don't forget that the RJ85 also carries 99 passengers in a single-class layout compared to the Embraer's (albeit I think the RJ85 is at 79 seats with BACF?). I think fuel needs to go up quite a bit more yet before the cheaper capital cost of the RJ85 is outweighed by the Embraer's lower fuel burn (and maintenance cost).
Cheers