Ironically, the V2 program was a net detriment to the Reich. It consumed vast resources that would have been far better spent on conventional weapons. The V2's problem was it was hopelessly inaccurate (the guidance system was a clock and a gyroscope) and did only insignificant damage to the Allied war machine.

The V1 was more cost effective - not because the V1 did much damage, but because it diverted a great deal of British effort at trying to shoot them down and blow up their launch sites. The Germans eventually figured the latter out, and built lots of fake launch sites for the RAF to uselessly destroy.

Missiles only became effective due to better targeting or nuclear warheads.