I have been looking at some interesting places to go, and Greenland came to mind. Pricing flights online, it looks like a flight from Copenhagen to Kangerlussuaq round trip goes for over US$1000. (This is before factoring a flight to the capital Nuuk which would be about an extra $250 each way). Much of this is due to the fact that only two airlines serve the region and they can pretty much charge what the market will bear.

So what is your most remote trip destination served by commercial air? I was lucky enough to get out to Easter Island on a OneWorld RTW, and that is about 5 hours from Santiago. Had it not been for the RTW ticket, the price would have been in the neighborhood of $4000 in business. That is probably the most remote for me, with Barrow, AK and Ushuaia, Argentina being runners-up.