You can get a very safe ECE 22.06 rated helmet for $100-150. The more expensive helmets are lighter, more comfortable, have cool designs, and nice stuff like transitions visors or Pinlock anti-fog, but aren't really any safer until you get into FIM fhpre-02 rated helmets for MotoGP racing. (fhpre-01 is functionally identical to ECE 22.06)

The days of having to shell out $600 for an Arai or Shoei for superior protection are past us.

Wow. That's awesome! My helmet back in the day was indeed a Shoei. I don't recall for sure, but I don't think it was even the absolute most expensive model at the time, but it was about the cheapest helmet I felt comfortable trusting my life too.