+100. Ear plugs are just as important (arguably) as all your other safety gear. As far as cost, I got some custom molded ones (Westone brand: http://www.westone.com/hearing-protection-products/custom-fit-hearing-protection-products-1) for $100.
Think of it this way, how much is your hearing worth? over time, wind noise at 100+ mph can do serious damage.