Nuclear bomb, WW2 stuff
This is actually a special scenario. This was not just "Can we have some money to make some bombs that we can only use once but cost a lot but basically wipe out cities?"
This was "Okay, we know that our enemy already knows about this, and we know that they are working on it. We need to complete it before them, if only to hold it over their heads and force them to surrender before they do the same to us."
"Our enemy" being Germany since Japan was out of the loop. Vast amounts of time, effort and resources were spent in the information, espionage and special operations part of the war to stop Germany from producing nuclear weapons and spreading misinformation about the best way to produce the material needed to make the bombs. The monetary cost of developing the weapons was pretty much a non-issue; if we didn't spend the money trying to make it as quickly as possible, we lost. Now, with historical information and hindsight available, this wasn't really the case as our other operations and Hitler's reluctance to rely on "Jewish Science" proved sufficient to show that we were safely in the lead. However, hindsight also shows that it was
really, really close to Germany figuring it all out and beating us in the race.
The equivalent for space would be like someone pointing out, "Hey, I figured this thing out! We could make the Death Star laser with this!" and everyone going "Yeah, we just have to figure out which way is the best to make that stuff you found!" while everyone is at war. It's not a question of "Is this cost effective?", it's a matter of "If we don't finish this R&D first we lose and are potentially all killed."