“More recently, the twenty thou needed to fly the leader of her prop-up party back to Northern Ireland by RAF transport was instantly available.”
The £20k is a ridiculous over-statement.
The cost of fuel for a Boeing 747 flying from London to New York is about £25,000. For the same aircraft to fly from London to Belfast would be about one tenth of that. For an aircraft of the type used by the RAF for such trips you can probably halve that amount. So let’s say, conservatively, £3,000 for the return trip. There are no other costs involved apart from a bit of between flight maintenance (no labour costs). The RAF already owns and maintains its aircraft, its crews are paid regardless of whether they fly to Belfast or not, and no airport landing fees are involved. And all this assumes that the aircraft was used solely to ferry Ms Foster and that all the costs are attributable to her.
The £20k quoted is what it would cost if an aircraft was chartered privately and is an inappropriate comparison. To understand just how daft such a comparison is, you can charter a private jet (something like a Cessna Citation 7 seater) from London to Edinburgh for about $6,000 (£4,200) and that includes all commercial costs.