CDs are the current punkest physical format. They are cheaper to produce than cassettes even. You can listen to them in your car. CDs are not dead to serious music collectors, and are in some ways superior to vinyl (not in the dynamic range department, however).
Not cheaper for very short runs. I know friends who will put out cassettes with as few as 10 copies. CD production doesn't get cheaper until you're talking larger quantities (like 100+).
