I read just now that the V-1 and V-2 programs cost 50% more than the Manhattan Project. Given that the Manhattan Project had many Soviet spies, I was wondering if there is evidence of infiltration of the German program by Allied agents during the war (as opposed to Operation Paperclip collecting data and expertise afterwards). I know that the existence of the program was obvious as soon as the first V-1 was launched, but I'm curious about anyone getting construction or engineering details to the Allies.
Also, if there wasn't any such infiltration compared to the Manhattan Project, why? Was it mostly attributable to the Nazi use of concentration camp prisoners for labor? Or were espionage assets simply directed at more urgent goals (i.e. D-Day preparation) over the less than effective V program?
First, it's worth remembering that the Soviet espionage of the Manhattan Project was Ally-on-Ally spying. It was not the same as Ally-on-Enemy spying, which is generally harder for a lot of logistical reasons (e.g., the Soviets could funnel their espionage back to their embassies using couriers, whereas the Germans and British lacked embassies in their respective countries during the war). The Soviet espionage was also a case of "moles" — internal scientists who were working on the project (quite diligently and honestly) who were also sending some information to the Soviet Union (because they thought the Soviets could use the help, and because they thought a world with an American monopoly on nuclear weapons would be unstable).
There were several technical spies within Nazi Germany helping the Allies, but it seems a much more rare situation, to have someone get to that rank of importance that they would be let in on such things, yet be secretly opposed to their own country (in contrast with "also supportive of another country" in the Soviet-US-UK situation).
Anyway, the only Allied intelligence on V-2 that came from people inside the Axis areas that I know about is information sent to the British from the Poles (who also sent information on cryptography as well). The Germans were testing V-2s in Polish territory early on, and some members of the Polish resistance were able to smuggle information to UK sources. The result was British raids against Peenemünde, which apparently slowed down some of the work there (part of Operation Crossbow). So this is not quite the same thing as the Manhattan Project style of espionage.