Riolu

The cheapest copy at £7.99 has been sat unsold for 11 days, so undercutting it should move your stock first. Be aware that the LP-flagged copy at that price is a condition concern — a clean example can ask more. The 30-day range ran from £15.37 to £20.50, so there's room between market lows and your £21.50 price. Grade only flawless copies for PSA, since the gap between a PSA 10 and 9 is stark (£634 versus £39.86, a 15.9× multiplier), and don't expect asking prices on high grades — five of the last six PSA 10 sales came through accepted offers rather than the sticker.

• NotableThe cheapest copy has sat unsold 11 days at £7.99. Undercut it to move first.
• CautionA PSA 10 is worth 15.9× a 9 (£634 vs £39.86); only grade a flawless copy.
• CautionThe cheapest copy (£7.99) is flagged: graded LP by the classifier. A clean copy can ask more.
• NotableAt its 30-day low of £15.37 (the high was £20.50).
• Notable5 of the last 6 PSA 10 sales were accepted offers, not asking price; leave room to negotiate.
• NotableUK asks run from £7.99 to a £22.54 median; the cheapest is 65% under the middle.