A similar MAX Nissan rod set is $180 - this one is a single rod but still uses 2 pillowballs which is the most expensive part of a rod. so $120 sounds like a reasonable price.
I doubt we will make RX7 rods (at least anytime soon) because we have our resources committed to more pressing developments at this time.
I don't know much about engineering but I don't think it'd take too much effort for MAX R&D to produce these badboys. In anycase when the time comes it'd be a nice addition to the catalog.