How RAM usage effects battery drain? I'm really confused about Android memory management.

I just read here that killing apps by swiping from recent list or using task killers won't save your battery but drain more because this cause the OS to load the apps all over again next time you launch it or startup by themselves. They also said the actually thing we should worry is CPU usage, not RAM usage.

Is that mean using too much RAM doesn't drain battery? As RAM is a hardware, holding something on it shouldn't drain battery? What if I was playing Temple Run and just press home button so the app will load faster next time I launch? Or should we just press back button until the app exit as we always do? I've also searched the internet but some said it would drain battery as it sits on RAM, some said there is no difference between RAM holds actual data or nothing. Should we let go of our app-killing habit and just feel relax? 

Some precise answers would be greatly appreciated. Thanks. :)
I doubt that there is a direct correlation between battery consumption and RAM usage. The hardware doesn't know which RAM cells contain 'used' data and which not. So there can be no difference in battery consumption on that level.

But I think that one could say that unnecessarily killing Apps causes a few extra CPU cycles when those Apps have to be re-started and therefore "uses more battery".

And yes, you definitely should let go of your app-killing habit. In most cases, Android is capable of managing the system's resources quite well and you shouldn't bother with manually killing Apps. They definitely won't drain more battery if they just idle around and consume some RAM. Of course, if those Apps are constantly using the CPU, they will drain battery (but this is usually a sign of a bug within the App or a badly implemented App).