NuMI cost $139 million to construct, including the detectors. It was driven by the Tevatron, a proton accelerator 2km across that itself cost $197 million to bu

NuMI cost $139 million to construct, including the detectors. It was driven by the Tevatron, a proton accelerator 2km across that itself cost $197 million to build in 1991. 150 GeV particle accelerators are not cheap, and are going to be impossible to build secretly. If everyone knows you have a phone to the future, finding counterparties is going to be hard. Who's going to take the other side of a trade you know you're going to lose?