The Ares Alpha is 11F, and the Yamaha Raiden is 14F. The Rain Forest Carbine, however, is 8R, and thus the most powerful Restricted assault rifle.
ZC, what does one have to do with the other ?
Well, you compared it to two other weapons, so I noted there's another comparison to make: unlike the Alpha and Raiden, you can be seen in public with a Rain Forest Carbine without people trying to arrest you solely for owning it.
They are illegal because of those toys/attachments on them. And those things have a price for them which is why the weapon costs more.
You're not exactly correct there, actually: the HK-227 and Ingram Smartgun X (and to a lesser degree, the Ares Light Fire 70) are Restricted despite coming with an integral sound suppressor, and the Restricted Remington Suppressor ships with a detachable sound suppressor, even though sound suppressors are normally Forbidden. While it's true the Raiden and Alpha were made Forbidden by the developers to offset their high stats, it's not like you can strip parts off an Ares Alpha while keeping the damage stats and turn it into a Restricted weapon. Legality is also a feature worth paying for.
Now, I don't actually have an opinion on the nerf itself or on the price of the nerfed version (although martin's idea of keeping it a bit stronger but dropping not just the FA mode, but also the BF mode, sounds interesting), but I don't think it's fair of you to snap at me for merely pointing out you're not seeing the whole picture.