Some drivers in Spec Miata have complained quite a bit about the cost of engines now that SM has been a national class for a couple of years; they seem quite sure that the expensive motors (ca. $8K I hear) must be illegal or something.
As for my thoughts, well, some Showroom Stock drivers have been paying those kinds of prices for nationals motors for years.
"I am shocked to discover that there is parts bin based balancing going on in a Showroom Stock based class." -- Claude Rains, Casablanca