Hi and welcome.
Starting with probably the most expensive - the Cashmere scarf. This is a large scarf (sorry, can't remember the size). There are usually one or two designs each year. Expect to pay over £500 for one.
The most common Hermes scarf is the silk 90x90cm Carre. This can by tied in a variety of different ways (when you buy one, ask for a guide on how to tie it..it used to be a small book but recently changed to a set of cards - though some shops still have the books as I was given one at Barcelona). They are about £200
Then there is the pocket square which is smaller 45x45cm. These retail about £75.
Next is the twilly - a long narrow strip of silk similiar to a man's tie. These can be tied round your neck or wrist or attached to your Hermes Bag (if you are lucky enough to own one!). These are the cheapest Hermes scarf and cost about £70
There is the Plisse which is the large square scarf which is folded back and forwared to give a concertina effect. If I remember correctly, they are about £220.
There are also cotton scarves but don't have any of these (yet!) so not sure of sizes or prices. The Hermes website will show the different styles available with the costs. There are two "collections" of scarves released each year and some styles become highly collectable.
There is one small problem...owning one will never be enough...once bitten, you'll be lusting after the next, and the next and the next....