During the Scottish Independence Debate between Alex Salmond and Alistair Darling, Mr Salmond alluded to the Trident nuclear weapons at Faslane and stated that £100,000 million (i.e. £100 billion) is planned to be spent on them "over the next generation", of which £8 billion is "Scotland's money" (by which he of course means is the equivalent forcibly extracted in tax from individuals living & working in Scotland in order to pay for this expense).
He's not explicit about exactly what time frame is a generation. Assuming a generation is say 30 years and taking these figures on face value, that means £3.33 billion per year, of which £270 million per year is coming from Scottish taxpayers.
The UK government budget 2014 estimates total expenditure of £732 billion in 2014-15 (ignore for now that they also estimate revenue to be only £648 billion - if you earned £648 per week would you think it a particularly sensible policy to spend £732 per week?)
Scotland represents approximately 8% of the UK in population terms, so assuming similar patterns of taxation and spending as in the UK as a whole (it's not going to be exactly the same, but it'll be close enough for my back-of-the-envelope estimate), total government spending in an independent Scotland would be circa. £59 billion.
£270 million is less than 0.05% of £59 billion - that's a rounding error! It's about 50 quid per person per year.
To put this into perspective, the UK government is forecast to spend £222 billion on 'Social protection' this year alone (this includes state pensions, child benefit and jobseekers allowance) - that's billion with a b. This works out at over £3400 per person. That's 68 times larger (or two orders of magnitude larger) than spending on nuclear weapons.
Believing that Scotland should get rid of it's nuclear weapons on the basis that you don't agree with them on moral grounds or on other principles is one thing, but to argue for getting rid of them on the basis of cost is a very weak argument indeed when their cost is so much smaller than so many other things the government spends our money on.