You make a good point on "off-the-shelf" technology being a key factor in keeping CATS prices low.

There have been commercial developments that help space transport designers.

Due to advances in electronics, avionics are far cheaper, more reliable, and above all, smaller and lighter than ever before. When I started in this business, avionics was one of the most expensive development items. It's still a tall pole in the tent, but it isn't the pain it used to be. Guidance and navigation have been drastically improved by GPS and other technologies.

Composite technology is a big weight saver, although it has some drawbacks, and formulations have been developed that are even LOX compatible.