Gizmodo summary
There's an ArXiv paper
It's a Trap: Emperor Palpatine's Poison Pill
Although others have worked out the cost of building a Death Star before, Feinstein decided to start from scratch, estimating the amount of steel and other raw materials required to build the planet-destroying weapon. After factoring in research and development, he arrived at a total cost of $419 quintillion dollars for both Galactic war machines.
That figure may sound mind-boggling, but we should remember that Emperor Palpatine had an entire Galactic Empire’s worth of assets at his disposal. Feinstein, for his part, was more interested in learning how the Imperial banking system would respond if the largest construction project in the Galaxy was suddenly destroyed. Popular Science explains his findings:
Following logic stitched together from prequels and Wookiepedia, we get a galactic banking sector with assets that are 60 percent of the gross galactic domestic product.
[Feinstein calculates the Galactic GDP to be roughly $4.6 sextillion per year.]
Since these banks are likely heavily invested in the Empire itself and the Death Star specifically, the destruction of one Death Star by intergalactic terrorists and the collapse of the Empire following the destruction of the second, would devastate the galactic markets, and create a financial crisis on a truly massive scale.