you should check ebay, when i had a nintendo ds i bought a video player that u could stick compact flash cards in, and i got a 1.0 gig CF card for about 70 bucks, so i wouldnt imagine a memory stick being much of a differnce in price.
Memory sticks are a special format designed by Sony and often can cost as much as twice the price of other flash storage devices. Actually the PSP seems to have really driven down the price of memory sticks or maybe I never watched the prices enough to notice.
My monitor shows $239.99 for the Sony 1G and the SanDisk at $339.95; interesting a 2G Sony is $346.95. Man do I regret not going with the Dell deal. I saw it there a couple weeks ago and didn't jump expecting that it would be still be there. Now, like someone else mentioned, there is no such product on Dell's site anymore. AND...the shopping continue's for another sub-$100 1G deal.