The five rarest 50p coins revealed including Kew Gardens and Olympics ones

The Royal Mint has struck a special 50p coin to celebrate 50 years since decimalisation. This coin won't be released into circulation, but what are the rarest and most valuable ones which have? https://www.dailymail.co.uk/money/saving/article-9150781/The-five-rarest-50p-coins-revealed-including-Kew-Gardens-Olympics-ones.html?ns_mchannel=rss&ns_campaign=1490&ito=1490