Antispam appliance vendor Sendio just received $3 million in funding. I have had a hard time with the Sendio solution in the past but all my problems were due to a corrupt database which the company fixed remotely. This device is a great productivity booster and I recommend it to anyone who wants to boost productivity.
When you first turn the appliance on you need to initially mark all your good email and senders but once done you don't need to mark emails from good senders again.
The savings you find is due to the time you used to spend having to go through spam in your inbox. Instead, you check a web portal the device provides where much of your bad email now lives. Over time, less and less "good" email stays in the device, making this solution more useful over time.