Coilovers are expensive because of the engineering and materials that go into each individual coilover. It's not easy to design a coilover that's flexible enough to meet your users performance and ride quality goals, is built with materials that are both lightweight and durable for years of use, as well as fits and bolts up to your users vehicles without modification. In short, they're more money than drop springs because of the effort and level of expertise required to manufacture them.
