True, but you could say the same thing about almost any JIT compiler/interpreter for a garbage collected language. It's not like java is known for it's memory efficiency. I'm not too knowledgeable about the memory efficiency of v8, I imagine they pay attention since it's in a browser, but I'm going to guess compared to a simple interpreter it's probably not great.

That is of course true, but pypy does have an unusually large memory burden (and the developers do know about it - it's just not top priority at the moment).