$ony does charge a premium for their
(rebranded non-oem) memory products.

Many of the memory company out there
never actually produce their own memory.
Its usually a larger chip company from the
east who then re-sell/re-brand them to other
national brands.

So when you buy that cheaper 1GB ram module,
from xxx and compare it to the more expensive
yyy company you could actually be getting the
same 'quality' The only problem is discerning
the quality from right chip manufacture.

I never heard of 'Elpida' - sounds like a salsa
company. But you can ask them, where their chips
are from you might have a better idea of quality.

NEC, SAMSUNG, TOSHIBA, and a few others I can't
recall are all good chip manufacturers. Many come
from Taiwan.

As for your "1GB DDR2 PC4200 533MHz..." I don't think
that spec is inline with your particular sony
manchine. PC4200?? I believe Sony maxes out much
lower than that. Even if you used this, it will
only run at the machines oem max. But you could
also create a problem if the onboard ram specs out
differently than the one from Elpida.

Be safe, use similar brands if you can afford, or
at the very least, same specs.