Actually I only paid $150 from Aim Surplus for the RGun's BCG. The only difference I can find between the two is the gas key screws. It looks like Fail Zero uses stainless hardware. The RGun's BCG has a better stake job. I can post a pic later if anyone is interested.
I tried calling RGuns to get more info about their BCGs... HAHAHAhaha
That is 45 seconds of my life I'll never get back, I will definitely never order anything from them directly.