While I do like the Ki-84 and don't think anything is wrong with it, although it can take a beating. I think that the 4x20mm would, obviously, be perked. As for the price, I would say between 40-75 perks. I'd think that as fair. Considering the tempest has 4 20mm and packs a punch, but isn't on the 'same level' as the ki84 for dogfighting.