The lower memory models are cheaper right now because of "quantities of 
scale".  Usually it cost more to purchase with one DIMM.  In 2 years, the 
same question will be asked about 512 MB DIMMS and 1 GB DIMMS  :)

You can buy one 512 and swap one of the 256, then you will have an extra 256 
to keep or sell.
-- 
Thanks,
TheBurgerMan
at
gmail.com
--
"Lee" <lbray5032@bellsouth.net> wrote in message 
news:D%81f.13$0l.0@bignews1.bellsouth.net...
>I have a Toshiba Satellite A45-S150 which has 2 slots for memory, mine 
>presently has 512K memory installed in a pair of 256k memory sticks. My 
>question is as follows.
>
> 1.  Why do the manufacturers install 2 sticks instead of just one?
> with one stick of 512 it would be so much easier to upgrade say to 1 Gig 
> of memory!
>
> 2.  Is it feasible just to buy 1 stick of 512 and leave one of the 256 
> sticks in or do they have to match?
>
> Or is this just a way of making money in upgrades?
>
> Lee