It's only a limited to a question of cost if you compare like with like.....
Going to have to completely disagree with you there. Cheaper is cheaper regardless of any comparisons..................whether cheaper is good enough is still up for question.
However if you are only going to consider cost if you are comparing like with like then you're both narrowing the debate incredibly, and probably being rather unrealistic.
The question remains would an RAF based deterrent offer sufficient deterrence regardless of whether it is as much of a deterrent as Trident, whilst costing less. Refusing to consider non like for like options is ignoring the question.
And one has to wonder whether not having an
independent nuclear deterrent is much of a deterrent at all..............................