The real question is: will The Pokmon Company ever print enough to meet demand, or will fans always be fighting to pay a fair price?
Either you played it normally or you could have it come into play with a +1/+1 counter and it gained "must attack each turn if able." My one suggestion was to shift the negative from the red "must attack" to the black "can't block." I felt that it would be better flavor, would play better, and would create fewer bad feelings for the players (as a rule, players dislike when their creatures are forced to do dumb things that get them killed)
Essentially, if you open any Ancient Tomb in your Edge of Eternity pack, you're going to be happy
Regardless, like others mentioned above, whether there are just 50 or 500 copies in existence, they are very rare cards with almost no supply but a reasonable[1] amount of demand
Its limited availability and exclusive distribution make it a valuable addition to any collection
this helps investors analyze price trends