Ryan2000, your last sentence is accurate but the withdrawal of many of the airlines listed has nothing to do with the costs of operating at SNN.
The market to Canada from to/from SNN is much more Air Transat than Air Canada. When AC had to serve SNN to allow access to DUB, it did. When that neccesity was removed, AC went. Royal Jordanian moved from Amsterdam to Shannon for the fuel stop when its A310s didn't have the range for direct Amman - US flights. It didn't have fifth freedon rights at Amsterdam and SNN offered cheaper handling. It also got fifth freedom and the empty seats it sold ex SNN were a bonus. When it bought A340s the need for the fuel stop went away.
PIA decided on SNN over MAN when its MAN base was tiny. The decision was political within PIA and caused ructions up to government level. The airline was ordered to operate through MAN and then achieved various economic benefits of scale, as well as access to a Halal kitchen so food top ups could be made if necessary.
Aeroflot only served SNN when its aircraft didn't have the range for direct flights. Aer Rianta capitalised on the need by doing the fuel farm deal. The need has gone, so has the airline - again the seats it sold was a bonus at a time the USSR and the Russian Federation needed hard currency - something it now has in bundles.
As you are very well aware the Aer Lingus decision was nothing to do with cost. The route was extremely profitable. The decision was "political" as Aer Lingus was determined to have a slice of the Belfast market and didn't have the slots without ditching SNN. The performance of the Belfast base is nowhere near as good as hoped.
The World Airways decision was a security decision after the peace campaigners' actions. As far as is known, US trooping flights don't pay the normal handling charges.
CentralWings was going down the tubes when it withdrew - as it did from many other stations.
Aer Arran's service was a reaction to Aer Lingus withdrawing ticket sales on the DUB-SNN sectors of transatlantic flights and their total withdrawal of the domestic service. Aer Arran didn't even try to make the route work with poor timings and poor marketing and Aer Lingus relented and sold tickets on the sector after one summer so Aer Arran gave up.
Thompson to Coventry was a joke. The early morning departure meant a 07.40 check in at the latest - OK if you live in Limerick or stayed at the Gt Southern the night before, useless otherwise and, at Coventry, if you were lucky enough not to have to walk 150 yards in pouring rain - as happened when I used the flight - you still had a tiny arrivals area, a half hour wait for the only bus for Coventry to connect to Birmingham etc, and like as not you would have to queue in the rain.
With FlyBe, easyJet, American and Virgin Express you may well have a point but Hapag Lloyd were well and truly shafted by O'Leary.