There seems to be a big range of prices that one can pay for a cycle helmet. They seem to range from around $30 up to several hundred dollars! What does a $200 helmet do that a $30 one doesn't? Spare me the $2 head , $2 helmet jokes...

More expensive helmets have more advanced retention features like Specialized's Brain Trust 2 system. They have more expensive manufacturing processes to mold the hardshell and styro together or more as one unit. Cheap helmets usually have the hardshell "skin" stuck on top of the styro.

They have more sophisticated and better looking graphics, materials, finish and are usually the best a particular company can make.

Proper fit and comfort are most important as any foam helmet will protect about the same. However, an ill-fitting helmet will not do it's job so if you can only get a good fit with a $100 helmet, buy it. If you get a comfortable helmet you like that fits well for $30, than buy that.

200$ helmets are usually full faced. That should be a self explained advantage.

Expensive roadie helmets may be more aerodynamic but since I don't care about pure speed in that capacity I don't do the research

Cheap helmets usually have less whole / ventilation which is a big thing to some people. Style too. I find cheaper helmets 'generally' make people look very phalyc.

As for protection. Not a diff, they are all standard.

I will take issue here. It is true that they all have the same minimum protection standard, but that standard does not tell anything about how much the helmet exceeds that standard.

I was stupid one time and messed up a $50 helmet with some solvent based glue. I decided to get another helmet and eventually used the damaged helmet for some backyard testing.

I can safely report that the higher end helmets with the bonded microshell (like most companies higher end road and mountain helmets) will stay together after an impact. The polystyrene will crack, but the bonded shell holds the pieces together. This effectively means that if the helmet is still held in place on the head after an impact, it will still be around to absorb a second (in a different spot of course).

I also know that a helmet with a taped shell will shatter on impact and is not around to absorb another blow as my father (John Ratliff who also posts here) found out when he had his recent accident.

This is one of the problems with the bike helmet industry. Since the design of all helmets are carried out by private companies, the companies are hardly in a position to say whether one helmet in their line is better than another, much less how much better. All they can say is that all their helmets pass a minimum standard. Thus the consumer has no information about which helmet to buy other than vague statements like "best used for road," and price.

I have seen protection ratings for laptop computer bags, but could you imagine trying to choose between a "superior protection" $150 helmet verses a "minimum protection" $20 helmet if you are tight on a budget?

One of the major reasons that the expensive helmets (some Giros, especially) cost so much is advertising! They spend many $$ sponsoring teams in order to have their name seen.
Several years ago, Consumer Reports tested the protection of various bike helmets (not the style or durability, though). The highest rated helmets were the cheapest, taped-on-cap style Bell helmets, costing about $30 each. Many of the high-zoot $100+ helmets were rated not acceptable, due to chinstrap latches that failed in testing.

More buys you less. Weight that is, with better ventilation.

Other than that it's largely a style thing, but all the previous posts are correct at least to some degree

One thing no one has mentioned is the way the hardshell is attached to the foam of the helmet. On cheaper helmets, the hardshell is typically taped or glued on; on more expensive helmets, its bonded to the foam. I have no idea if this provides any more protection in a crash, but I find that bonded shell helmets tend to last a bit longer. I've had helmets where the taped-on shell begins to peel, or cracks at the edges.

**********? It's been mentioned in just about every post.