I find the gains to be really small as you pay more and more with helmets (other than aero helmets). I'm willing to pay $$ for an aero racing helmet, but for everyday riding I don't think you get much for jumping from the $60-$80 price range to the $200 price range. I guess if you ride with people who care about gear a lot and judge each other for their gear, it'll help you seem cool.
But for just comfort, performance, and protection, I think spending a lot on a helmet is a waste of money. (Although I might be convinced that Bontrager's recent WaveCell helmets actually DO offer better protection and could be worth the extra $$).
I find that Giro's basic MIPS models are fantastic - well ventilated, comfortable, affordable, easily available, easy-to-find replacement pads, etc.
Isode MIPS is dirt cheap and is great.
Foray MIPS is a step up and is also great.