Well, they can sell for 1/2 to 2/3 cost. I just looked at their site and they have quite a few in the same price range as Arai/Shoei. So the question is... what are you giving up at the lower price point?
I checked the busiest online seller in the US that carry all three Brands - Bell, Arai, and Shoei to see what full MSRP is on their top spec race helmets, here's the prices:
Shoei X-14 - $889
Bell Race Star - $779
Arai Corsair X - $979
Looks like MSRP shows the Bell is roughly 25% less than the Arai - not quite the discount I mentioned obviously.
The Bell has the following features:
Bell Flex Impact Liner, 3K Carbon Fiber Shell, Virus Jade Interior, Magnefusion Removable Cheek pads and the Panovision Class 1 Optics ProTint Photochromatic Shield.
Safety ratings are a grey area as most just list them as pass or fail and not best to worst.
Back to pricing, I see the savings differences as much more substantial for closeouts on previous year models with Bell than with Arai or Shoei - on the same website a closeout Arai is $579 and the same Bell Star is $399 - over a 40% savings.
Arai and Shoei are similar to brands like Sidi boots, Oakley sunglasses, etc.. where they have very strict online discounting policies - they never allow retailers to advertise super low prices unless given pre-authorization.
As always with Helmets, my recommendation for people is to try it on in person, leave it on for a while if possible - 10-15 minutes, and buy something you feel comfortable with, not something you think looks cool, your Hero #46 wears, or is heavily discounted and you're on a budget but isn't the right size or head shape.