[mjw930]

While there are inherent differences between helmets the large swing in prices is primarilly due to weight (advanced materials) and features (more luxurious interiors, vents, scoops, etc.)

I would say that you should be just as safe in a Gforce as a Simpson.

Band for the buck I like PyroTect or the Bell M2. Both are under $300 in full face and are relatively light and provide decent ventilation.