This is a set of four cards, issued by Hongkong Post in 2021.  There’s no pre-printed postage (unusual for Hongkong Post), and our scan shows table tennis as just one of the cards; other subjects include bicycling, diving, and windsurfing.  The postcards are unused and still in their original cello wrap.  And why is this set so expensive?  As far as we can tell — and this is accurate up to the time we write this — the cards were never put on general sale, but instead made available as a bonus item redeemable by subscribers who had enough points from the Post Office’s annual subscription programme.   None of that matters to you, of course, but unless things change, there will never be many of these sets available.  Anywhere.  Grade: 1