Actually, about 9,250 V1's were fired against London, but less than 2,500 reached their target. In flight they were almost as vulnerable as their ramps: about 2,000 were destroyed by anti-aircraft gunfire; 2,000 by fighter planes, and almost 300 by barrage balloons. The V2, on the other hand, resulted in about seven thousand civilians killed in London by the V-2, an average of over 5 deaths per attack. (Source The German "vengeance weapons" - V1, V2 and V3). Again, even one death was catastrophic for that person as well as England as a whole, but on a purely military assessment, Its guidance systems were too primitive to hit specific targets, and its costs were approximately equivalent to four-engined bombers, which were more accurate, had longer ranges, carried many more warheads, and were reusable. Moreover, it had diverted resources from other, more effective programs. The cost of the V2 program are estimated to have been as high as $21 billion in 2005 U.S. dollars...
Nevertheless, it had a considerable psychological effect and as such was effective. And, as stated, each death took far more of a toll than its own immediacy...