It weighs three factors: regional and national tournament wins, how long the leader stayed meta-relevant, and how aggressively Bandai restricted its support cards (a strong signal of dominance)
When you move them onto another creature, they'll double again to 12 +1/+1 counters
Its estimated price is around $500,000 and above, and this also varies with the increase in its quality
Of course, those who prefer to build their own decks for executing a particular strategy, trying out a new idea, or simply following a meta build can still pick out each card one by one
This is exactly how they found all of those original Legends boxes from 1993 that they used for Dominaria United - They had tucked them away in some warehouse
I am not sure how popular the e-Card+EX format is for TCGOne players, but there is at least one meta-relevant card for the EX format that is effectively mistranslated