The UltraGB+ 250GB retails for US$399.95, and the 500GB model retails for $799.95.
Also available is the ComboGB pocket drive, focusing on the needs of iBook and PowerBook users. The ComboGB is bus-powered FireWire 800/400 and USB2 based on 2.5" drives. It is available in a 120GB 5400RPM model for $499.95, and a 100GB 7200RPM model for $599.99.
Note that using the ComboGB as a USB 2.0 drive requires a power adapter.