This cost would be much easier to calculate if every country reprocessed spent nuclear fuel like France does instead of storing it. Reprocessed MOX fuel costs almost ten times as much as enriched uranium, but the left over waste products decay to levels similar to natural uranium in 300 years instead of 10,000. Molten Salt reactors would probably make reprocessing cheaper.
Yeah, Britain did that. The reprocessing plant has turned into another money pit full of leaking pipes and dubious practices, with a multi-billion pound decommissioning budget.
Plus, as you suggest, no-one wants to buy the MOX fuel product because it's more expensive than enriched uranium.
