Creating nuclear weapons most likely requires a great deal of knowledgable people and some heavy equipment. The amount of money it costs to get the experts together and give them the require materials is probably a great deal. I believe it is in fact a good part of the drain on the economic situation.
Nuclear weapons are an economic burden, but they're also a burden on the survival of the human race. In reality, nuclear weapons are never going to be safe, and there is no reason these devices should even exist. They are not adequate for defense, since their continued existence will mean the end of the human race itself.
The financial benefits of a nuclear weapons program means that a country is less likely to be invaded by another or attacked. Look at the case of North Korea, if they did not have a Nuclear Weapons program the west would have attacked to topple a wicked regime. But by having such weapons the people in power can hold on to their country. An extreme example maybe, but look at Israel, no one knows for definite that they have them but everyone suspects that they do, if it wasn't for this probability then the Arab countries that are against the very existence would have destroyed it years ago. So from a National Security point of view they are worth it.