The Pikachu (SWSH020) card can be found in the Swsh Black Star Promos set.
Recently sold 10 times and based on those sales is worth around £20.76.
Currently, there are 6 open listings for this card on ebay.
This card sells in the range of £7.08 to £34.44, making it quite volatile.
This Promo card was illustrated by Hideki Ishikawa.