Corsair is probably slapping what couldn't run at 4-4-4-5 speeds @ 2.40v and instead they pass a different test and they got the results they wanted and sell them at that price. After all, for most people, they would think that CAS 4-4-4-5 is way better than CAS 5-5-5-15 but that's not the case in reality for DDR2.
It's just like picking CPUs, Intel test a group of Conroes and if they don't pass the extreme test then they move to the E6700 speeds and if it passes that test, it becomes E6700. And so on.
For RAM they have a lot of speeds to test and can change the timings and voltages, whereas with the CPU, there's only one way: stock speeds with a "pre-set" voltage.