Like most Pokmon cards, the value of Meganium depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Expedition Base Set)
Upon further investigation I have found that every single PSA 10 card graded of these 2 cards (that Ive been able to find photos existing online) are mislabeled
Even if the highest potential for a card (its ceiling) is capped, it can have a high enough baseline (its floor) to make it consistently powerful
For the veteran collectors chasing pure nostalgia, The Pokmon Company is also bringing back the ultimate holy grails
Event Coverage - October 29, 2004 - Wayback Machine 25 More Random Things About Magic
It hits a good 75% of stuff and will have pretty full reign over the early game