Buy.com offers the SanDisk 8GB Memory Stick PRO Duo Flash Card, model no. SDMSPD-8192-A11, for $23.24 with free shipping ($2.91/GB). That's $6 under our mention in September and the lowest total price we've ever seen for an 8GB MS PRO Duo card.

Update: Buy.com also has the SanDisk 4GB Memory Stick PRO Duo Card, model no. SDMSPD-4096-A11, for $13.24 with free shipping ($3.31/GB). That $4 under our August mention as the lowest total price we've ever seen for a 4GB MS PRO Duo card.