https://www.bloomberg.com/news/articles/2015-06-25/a-500-billion-maybe-why-iran-s-big-moment-could-be-years-away
Maybe not necessarily but perhaps this…
Maybe an off the wall, but if the Pentagon can misplace 2.3T, maybe 500B for Iran came from HUD.
Urban renewal and all
https://www.dailywire.com/news/15163/ben-carson-finds-500-billion-billion-errors-during-joseph-curl