These are commemorative issue decimal Crowns and have a legal tender face value of 25p each.
The "standard" issue were of cupro-nickel and around 37 million coins were issued for the Silver Jubilee; around 27 million for the Royal Wedding. That being said, collectors may well pay a few pounds for one.
There were also issued around 200,000-300,000 silver "proof" versions of each of the coins which may be worth more like �20 (Jubilee) and �30 (Wedding).