So, right now, in terms of flash drive storage prices:
4 GB = 88. [edit, you can get 5 GB for $86: here]
1 GB = 38. [edit, $33 is the current lowest]
512 MB = 19.
258- MB = free to 5 dollars.
The 1 GB and the 512 ones can be found at eCost, I believe. Or maybe some other places. Mind, this is size in general, type not considered. USB flash drives tend to be slightly more expensive for the 1 GB / 512 sizes, since more people buy those. But if you go for SD cards, or CompactFlash, you should be able to find them at those prices above.
It's a sign of things to come~ expect more price falling.