Karnage
I-am-a-pirate. I do not need credentials!
The 700/900 are probably cheaper thanks to the narrower tube and smaller profile, but my comment is more that as time goes by the 200s will soldier on while the 700/900s will, as they time/cycle out, be eventually be replaced either with similar sized EJets for which passengers and airlines have shown a preference or, in markets that can sustain them, smaller mainline jets.
Smaller markets will soldier on with the 200s which are being cycled through the desert in an attempt to prolong their lives. The idea that 700s/900s will flow down to smaller markets as 200s are retired is a bit of a fallacy. A 200 is cheaper to fly empty than a 700. Seat mile costs are lower on the larger planes because the added cost is spread out over more passengers and the passenger increase is larger than the cost increase, but the trip cost is higher. Good if you can fill those seats, but if you are flying around empty seats you aren't getting to use the seat-mile advantage of the larger planes and instead are spending more money to earn less. The idea among some regional crews that as mainline carriers get planes like the CSeries that 200/E145s will go away to be replaced with 700s/900s/E175s is a bit of a pipe dream. Yes, some markets will be able to make the jump but many will not. They will remain as long as the 50-seat jets are cheap to fly and maintain. Once that's no longer true it's not that the larger RJs will flow into those markets, it's that the regional airlines will either have to find a new 30-50 seat aircraft (outside of the ATR42 there's not much out there) or the routes will have to find alternative arrangements (think EAS 9-seaters).
