It does not mean automatic premium, mint, PSA 10, or guaranteed profit. Character demand, set, artwork, illustrator, language, condition, supply, and current buyer interest can produce very different resale outcomes among cards that share the same rarity label
The downward trajectory of the value of rare and highly prized Pokmon cards is on full display on price charting sites such as pricecharting.com, where for example, it can be seen that a PSA 9 1st edition Holographic Blastoise card from the Base Set which in February 2021, would have cost a collector a little over $8,000, has a value today of $3,750
As for reprints, the only one that's worth much is Skullclamp ($5), but a handful of others are quite playable, despite costing very little: Cranial Plating, Sharuum the Hegemon, Hellkite Tyrant, and Godo, Bandit Warlord are most notable
Awarded to the winner of the 2001 Asian Championships tournament, the Signed Blue-Eyes Ultimate Dragon was jokingly offered for $934 million dollars on Twitter by the winner, but later on a shop in Akihabara, Tokyo legitimately tried to sell it for $421,000