Its been a while since I last posted here, mostly due to my change in employer, as mentioned on my personal blog... Now that is settled, I have a backlog of things to discuss here. Also, I'll be at the Techshop pavillion at Maker Faire this Saturday and Sunday afternoons.
There is an interesting price graph for 2GByte microSD at Nextag. It shows an introduction at about $120 last September, trending down to about $25 now. Amazon has it for $25 and Amazon Marketplace for $16.50. Meanwhile, larger devices are shipping using the microSDHC format at 4GByte, and announcements have been made for 8GByte. The microSD format gives a performance of around 20MBytes/s, so for 2KB reads that works out at a maximum of 10,000 random reads/second. Writing at 6MB/s works out at a maximum of 3000 random 2KB writes/s. Even allowing for operating system overhead, several thousand IOPS should be possible at under ten cents per IO per second and $10/GByte.
Of course, most millicomputer CPUs interface directly to devices like microSD, so there is no support device or interface needed. Just a microSD carrier or two, per millicomputer module.