There's a SCOTUS case that says the government only has to pay a fair market value, not the "inflated by the government's need for the property" value. In the case a guy had bought a tugboat and fixed it up quite a bit. When WW2 started the government sought to buy it, and he insisted on a price well above the cost of the boat and the improvements, arguing that WW2 had increased demand so he should get a higher price.
So Musk would get a lot, but maybe not as much you'd think.
Fred Clark (https://www.patheos.com/blogs/slacktivist/) recently drew attention to John Hagee, a Texas preacher who's been preaching about the imminent Rapture since the 1980s. His church recently spent millions of dollars to start a K-12 school. Which really isn't consistent behavior if you really believe the Rapture is imminent.