$2 billion dollars for Hiroshima, and a similar amount for Nagasaki
The Manhattan Project, which produced the bombs, cost about $2 billion dollars from 1939 to 1945. That is about $24 billion in 2008 dollars.
For America 5 billion dollars For Russia 1 favor
See: Atomic bombings of Hiroshima and Nagasaki.
ALL NEW PROJECTS cost alot of money...to begin the project. After the product is built, then mass production can start; which, by it's very nature (mass production) entails cheaper prices.
Little boy the bomb used in Hiroshima was a uranium fission bomb. Fat man the bomb dropped over Nagasaki was a plutonium implosion type bomb.