Because the Pound is stronger than most other currencies. There are less British Pounds in circulation than, say, American dollars or Euros. Because of this, it takes more Dollars or Euros to equal the equivalent amount of British Pounds.
The British 2008 "dateless" 20 Pence coin may be worth Fifty Pounds, some people think it may be worth more. Some 'Proof piedfort in silver FDC" 20 Pence coins might get up to Fifty Pounds, but then, they cost a lot to buy in the first place. Most British 20 Pence coins are worth 20 Pence.
There were were fewer 1987 Ten Pence coins minted.
All British coins minted in 2000 are still in circulation. They are worth whatever is inscribed on them.
When talking about US coins silver dollars and dollars with the CC mintmark are generally worth more.
Yes. Silver coins are worth more than face value.
If you refer to the scrap value of the copper, there is no copper in British "copper" coins these days.
It is worth more since less are made :)
If they have been circulated, all British "New" Pence coins are worth whatever is indicated on them.
Coins in proof sets are generally worth a bit more than coins used in general circulation.
The British have never produced a Dollar or cent coins. Their currency is the Pound.
They are not valuable, they are still in circulation and are worth 50 Pence. Newer coins only have some value if they are in mint uncirculated condition or, if they are Proof coins. Due to the extra work put into them and the metals they are made from, Proof coins are more expensive to buy in the first place.
All proof coins minted since 1980 are worth more than face value. Most error coins which are worth more than face value.