The price for aircraft and spacecraft is almost entirely related to how much it weighs. A missile that's 10x heavier is going to be 10x more expensive, generall

The price for aircraft and spacecraft is almost entirely related to how much it weighs. A missile that's 10x heavier is going to be 10x more expensive, generally speaking, for a given nation. GBI is approximately 21 tons. A Minuteman III is approximately 33 tons. But you exclaim "The warheads are different!" It's hard to find the price, but an EKV is somewhere on the order of $20 million each. The W87-1 will cost somewhere between $8.6 and $14 billion for the entire program... not including the fissile pits that are being reused. This is still more per warhead than the EKV. Yes, the interceptors have to be more accurate, but they also use entirely different guidance systems. They don't actually have to travel faster, because they just have to be in the same place at the same time as the target, and the target can't really do anything to stop them. The problem with your statistical approach is that there's a chance that the target survives. And these are defined as must destroy targets. Places like launch control centers for ICBMs, Cheyenne Mountain for command control. Places you need to destroy to avoid them turning your own cities into self-lit parking lots. Because you aren't going to start a nuclear war to have a Pyrrhic victory. Because the point of the US nuclear deterrent is to turn you into a self-lit parking lot, on demand, in thirty minutes or less. And by making sure we can do that, we keep other countries from thinking that they can start using WMDs. Does it really matter that you destroyed Washington DC if you no longer have a country? The biggest advantage of interceptors is not that you saved a city that was targeted. Rather, you made the opposition make a choice on what would actually get targeted. A city blown up by 3 nukes isn't much different from one blown up by 1, but it's significantly different from a city blown up by zero. Example: back when the UK used V-bombers, they had 200 warheads targeted across the USSR. As Soviet defenses got better, the number of targets being hit was reduced. By the end of the Polaris program, all of the UK's warheads were targeted on Moscow. And I'd be surprised if there's only 90 must destroy targets in the US. Not that Russia has 1000 warheads, but the US also doesn't have 10 interceptors, because it was example numbers to make the math easy.