What's the real difference between cheap and expensive helmets? Is there any real difference between the cheap and expensive cycling helmets? Is it really worth buying a helmet at say 3 or 4 times the price of a cheap helmet? Will that helmet really give you 3 or 4 times more protection?
No, usually expensive helmets are lighter and more comfortable because have more ventilation.

So, if you plan to ride for long hours it's better to buy the more expensive helmet that you can afford, otherwise - for short rides - a cheap helmet will do the job.