On the private market side, we have apps like Whatnot with no publicly available sold data or again, the Facebook groups/marketplace, Instagram, etc
I sincerely, 100%, cross my heart and hope to die would choose 1,000 copies of any modern Charizard drop with unique artwork over a Pikachu Illustrator, even, if I had a gun to my head and was told to get the best 10-year return on a percentage basis
The standard practice on Reddit is to price things at 10-15% below TCGplayer or eBay comps, which might sound like you're leaving money on the table
Zacian from the Vivid Voltage set comes with a move meant to devastate VMAX pokemon appropriately known as Amazing Sword
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