In researching the topic, there don't seem to be many kit cars, outside of locosts, that use the miata. Very low quality parts, but some people love the adventure.
The spr1 kit can be bought for £3500 ($4600) which is a fair price for a good looking miata/mx5 based kit car.
Miata kit car. It was built from a 1999 donor and sports an fm ii turbo system as well as afco suspension. The car in this video is a sport kit fitted with the optional rear wing mounts and missing all the bodywork. But, they do look damn cool.