Any helmet you get from a shop thats of the same basic type (a lid as opposed to full facial helmets) will do the same job of protecting your head regardless of price more or less. The more you pay for a helmet, the lighter and better vented it will be. The more venting and lighter the materials used in making it, the more complex and thus expensive it is to make it. Thus the higher price.

I ride with a £35 helmet. I have no idea how much you should be looking to spend in your home country.

Helmets can make a difference in some types of crash. I would say it is worth the small expense and bother of wearing one. Others don't feel it is worth it. You need to decide which you think is right for you.

Even if you forget for a moment the dangerously bad drivers out there, your own error can cause a crash. Yesterday I didn't see a rather large stone and lost control of my front wheel. I was deaccelerating for a turn (across the other lane of traffic) and going at approx 20 mph. I had enough time to decide to lean hard left and throw the bike and myself into a nice soft verge full of mud and leaves. Bar a pulled calf, I and the bike were fine and my head was unaffected. But it goes to show how quickly something can go wrong. In the past, a helmet has protected my head from injury during a pretty serious crash in which I should of (but amazingly didnt) broken many bones.