LED torches range vastly in price from less than a tenner to hundreds of pounds.
Pricing depends on many factors but generally speaking the more robust the construction of the light and the more advanced the LED the more expensive it will be. After a certain price point you get into the realms of snobbery, custom builds, exotic materials, exclusivity, etc. Just like you do with knives.
Some of the deals on the Deal Extreme Website are excellent value for money. The lights are cheaply manufactured in China and badged with various names but are usually decent quality and use some of the latest LED technology.
The Tesco ones that have been mentioned are Chinese productions and are a good for the price, I seem to recall there are about three different models.
Only when the last tree has died and the last river has been poisoned and the last fish has been caught, will we realise that we cannot eat money