Economists calculate the cost of building a Death Star It would cost 13,000 times the world's gross domestic product (GDP), or £541,261 trillion, to supply the steel for such a structure while labour and other construction costs would send the price even higher. After all, they're both essentially floating weapons platforms so that seems reasonable. Building a massive space weapon is all very well, but you have to find the materials to build it with. The students also calculated that with all the iron in the earth, it would be possible to build just over 2 billion death stars. They warned, however, that most of the iron is in the core of the planet. They said: "Before you go off to start building your apocalyptic weapon, do bear in mind two things. Firstly, the two billion death stars is mostly from the Earth's core, which we would all really rather you didn't remove. Secondly, at today's rate of steel production (1.3 billion tonnes annually), it would take 833,315 years to produce enough steel to begin work. So once someone notices what you're up to, you have to fend them off for 800 millennia before you have a chance to fight back.