this is an example of a microdrive:
they are usually quite a bit cheaper, but the down side is that there is moving parts (can't be dropped) and the pic review time is annoyingly slow. however there is no noticeable difference in the speed during shooting. also the upload speed is slower.
i just bought a 1gb lexar professional for $32 USD with shipping on ebay. i'll let you know how the transaction went after i receive the package.
edit:
never buy refurbished electronics on ebay.