Spam is very cheap to send. The costs are insignificant as compared to conventional marketing techniques, so marketing by spam is very cost-effective, despite very low rates of purchases in response. But it translates into major costs for the victim.
A report by Tom Geller, Executive Director of SpamCon Foundation, estimated that the cost to send a single spam email was as little as one thousandth of a cent, yet the cost to the recipient was around 10 cents.
The overheads in sending spam are low. The main costs are: