What is the value of Charles and Diana coin 1981?

The coin, issued to commemorate the wedding of Charles and Diana, July 29th 1981, with a face value of 25 new pence, can currently be bought for around St£3.00. It was produced in (I think) 3 versions; 2 of them metal mixes, the 3rd silver. On E-Bay, bids start around 50p.