Value is determined by two main factors: the card itself and the error
Artist takuyoa followed in Mega Gardevoir ex's footsteps by not just depicting Mega Charizard in all its glory, but showing the entire evolution line, starting with Charmander, jumping to Charmeleon, and then the Charizard we all know and love
Once you reach their own island, they drop their disguises and are just regular Fortress trainers, while the Fortress leaders are the real bosses
Loose fur gathers in its stomach and serves as fuel for fiery moves
Sword of the Ages Starting off with a colorless version of fling, I cant actually imagine a worse version than Sword of the Ages without just straight-up making it cost a billion mana or so
This is a high price for an uncommon card, and were talking regular art Sol Ring, because there are serialized versions that are much more expensive