As someone that used to kit a pattern plane (Nemesis and Arch Nemesis back in the late 90's) I can speak to this a little bit. There are several issues. First is that a true "Kit" is not that much more expensive. Last real kit that was being sold was Mike Hesters Black Magic kits and those were about $600. That included a lot of Carbon Fiber parts that were expensive to make (I seem to recall that the carbon canopy had $50+ in materials alone) Even still, that's probably 50% higher than a similar wood kit might cost from Great Planes or Midwest. The problem there is volume. A good pattern plane might sell 100 kits over a several year period. A great one...a few hundred. In it's day, the Goldberg Ultimate sold tens of thousands of kit...annually. Not only is the market for a pattern plane extremely small compared to a sport plane, but the number of styles and designs is very high and constantly changing. A pattern plane might have a 2-3 year run before it's obsolete with rare exception.

The volume issue is huge when it comes to cost. The designers ability to recover a LOT of time in R&D getting a new design ready is very low. The ability to use high volume low cost manufacturing techniques is also very limited.

Lastly, the pattern plane community is extremely finicky and demanding about the percision of a kit and resulting plane which also increases the price.

Bottom line is that the pattern kit makers are not making a fortune. Unfortunately because of that, there are very few "Kits" even being offered. Everything now is in ARF form coming from overseas.