They are just SD cards with a different file format (Fat32 instead of Fat16 - standard SD cards). The costs are associated with flash RAM and that's dropping in price pretty good.
I found a 16 GB SDHC on Newegg for $51.00 which cost $180.00 in March and $350.00 last October when that size launched.
32 and 64 GB are releasing this year.
The rEVOLution is not being televised