His source is probably a Malcolm Gladwell tech talk [1] It is corroborated by other sites on the Internet [2], though Gladwell frequently gets his information from secondary sources so who knows if these are independent? Based on the history of the project though [3], it seems plausible - the Norden bombsight is basically an analog computer whose development started during WW1, and building a computer with WW1-era technology seems like it could easily cost half as much as building an atom bomb with WW2 technology.

[1] https://www.ted.com/talks/malcolm_gladwell/transcript?langua...

[2] http://warfarehistorynetwork.com/daily/wwii/the-norden-bombs...

[3] https://en.wikipedia.org/wiki/Norden_bombsight

Research and development, manufacturing, training, it ended up being fantastically expensive. Remember, this was a highly capable analog computer that had to operate in a difficult environment and even included a self-destruct feature.

http://warfarehistorynetwork.com/daily/wwii/the-norden-bombs...

> ...the cost of the entire program came to more than $1 billion.

So the Norden cost $1B (~$12-14B now), the Atom bomb cost $2B (~$25-27B now), and the F-35 today is ~$150B over budget. How's that strike you?