Only if it is in their interest. The UK and the USA, we are led to believe, don't pay ransoms.
A quick look at Al Jazeera, the best source of news on these matters, informs us that there have been innumerable killings of this sort-people of all nationalities, in particular Kurds. Sad times.
It is times like this when my opposition to capital punishment is tested to the extreme. That said an early exit to 'glory' is what these people are proud of. I think the rest of their life in solitary misery is more fitting.