Trans Intl. offers the ProStor 635i 3TB eSATA / FireWire 800 / USB 2.0 External Hard Drive for $148 plus $11.89 for shipping. That's $0.05/GB, tied with our August mention, and $30 below the lowest total price we could find for a similar quad-interface 3TB drive elsewhere. This 7200 rpm external hard drive features an aluminum casing, 64MB cache, eSATA and USB 2.0, FireWire 800 port, and FireWire 400 port.
Note that this drive is designed to fit under an iMac base, but can be used with any Mac or PC.