Dan,
My question is how much of your inter-island flying is connections from OTHER airlines? If UAL (who now has CAL in the stable) decided to bring 10 Dash-8-400s over from Colgan for example, and flew them for cheap carrying their own connections (from SFO, LAX, ORD, IAH, DEN, EWR, GUM, NRT, etc), would that affect your business? I know they already have nonstops from LAX and SFO to all of the islands, but the overflow or connections from the other hubs could help fill the planes, or allow their passengers to see more than one island on their trip. United/CAL has the money to do it, and the planes to fly it (Dash-8-400s have plenty of seats to offset the costs compared to a CRJ). If anyone can afford it and do it, I would say UAL could, and they have a NRT flight too that could allow Japan connections.
Bye Bye---General Lee
Can't give you an exact number but probably not the high. UAL flies direct now to the outer islands. But if they did try to set up their own feed with Turboprops, they would put themselves at a marketing disadvantage as most people prefer our 717's (any fare that gets put out by the competition will obviously be matched) United's product would be a UAL flight connecting to a turboprop on the other side of the airport vs our relatively seemless operation of connecting to a 717, not a very good marketing plan on UAL's part. Everyone they compete with would have connections to our 717's while they would offer the turboprops. They would also be spending a lot of money just to compete with their own direct outer island flights.