Federal makes all their hulls of Reifenhauser construction, but you can also cheapen up the plastic and use different materials for the metal. Brass plated steel is cheaper than real brass. Differences in hull quality affect performance minimally. Cheap hulls just aren't as good for reloading. This is the biggie.
Shot is the most expensive component of the shell.
The less shot you can get away with putting in, the cheaper the shell. Quality of shot is also an area for potential savings. I haven't looked at commodity prices lately, but the hardening agent used in most shot, antimony, used to cost around ten times as much as lead. There is a price incentive to use as little as possible. When you do this, you end up with softer shot and less reliable patterns.