While I agree with most of what Skipness has said, Stobart had to earn money on its domestic routes with, IIRC, factory-fresh ATR72-600s. The ERJs Loganair will be using are apparently owned by Loganair's mother company and will probalby result in very low capital costs, given their age. So the overall maths could work in favour of Loganair indeed (higher fuel and maintenance costs, lower capital and cabin crew costs).
Nevertheless, I am slightly concerned that Loganair now wants too much too soon and may risk its future well being and thus it core network in the highlands and islands (although I supsect that if push comes to shove, Scottish government will come up with something to guarantee the continuation of Loganair's core business).
As for ABZ-SEN, I find it interesting that everybody is focused on the competing ABZ-NCL-LCY service on Eastern. Another issue that has not been mentioned is the recent withdrawal of the ABZ-LGW route by easyJet which has removed 300 seats from the ABZ-LON market each day. Depending on where you live the southeast, of all the inconvenient alternatives to LGW (other than LCY), SEN might be a better option for some than LTN, STN or LHR.