I think it is

Charging for anything they can, dreaming up new ways to fleece us, using the unsociable redeye slots (i.e. the cheapest), and playing games when it comes to pricing. For your information Mr S'cabby, TC are NOT a low cost carrier - all the above things I would expect and accept from Ryanair but Thomas Cook is not low cost, as many people looking at their prices for this season will know. In fact, they can be one of the most expensive available, but still cheap quality service, poorly trained staff who never shut up from take off to landing and awful flight times.
It's all well and good people saying they hope they don't go bust as they are the only airline to fly to Dalaman from their local airport but that is no recommendation. If grass was the only foodstuff on the planet we'd all be fighting for a tuft

Let Thomas Cook go pop, it means the demand wasn't actually there or that someone else will step in and take their slots - and ABTC is a great alternative to TC. I would use them only if there was no alternative and due to the fact I'll happily drive to Manchester, Newcastle or use any of my local airports, I can normally find another way.