I'm not surprised that ISSCo generates most of its revenue from aviation. If you'd looked at the fares - minimum of £109 one-way for a 30-minute flight from Newquay to Isles of Scilly. How anyone believes that to be a valid comparison for IOM - where there is low-cost competition on the likes of LPL and LON and independent ferry competition - is beyond me.
I wouldn't have thought any airline could make the economics of IOM services work if they had to include empty aircraft positioning in their costings.