Helmet safety is standardized, so all helmets have to pass the same level of safety. Companies might say that their helmet goes further than others but they have no real legal claim to this.
So since safety is a given with helmets, the more you pay you get lighter weight, lower profile designs, adjustable fits, adjustable ventilation, etc. Are some companies trying to make a safer helmet? Yes, but they are not legally proven by testing agencies to offer more protection as of yet.