I've heard that junk mail and telephone solicitation gets about a 4% response rate (i.e., 4% of those who receive the mail or get the phone call actually buy the product or service). That makes it worthwhile for them to keep doing it.

I have a good pop-up blocker and a very good firewall, but some stuff still gets through. It's a never-ending battle. These folks regard blockers and firewalls as a challenge to be overcome.

Don Firth