<i>Putting aside whether I believe this is accurate or not momentarily, look at these conversion rate.</i><p>1% Response rate for unsolicited direct mail ('spam' - heck, I used to have that response rate doing real estate direct mail with actual letters!)<p>5% Conversion rate from responders to 'clients'<p>Average 'sale' $7,500<p>So 100,000 spam emails generate 100 responses, which is 5 'clients' and $37,500 in revenue. Return per email is 37c - with a negligible cost to harvest and send it's little wonder my spam filter works so hard.