The difference is that while they have an ink cost on them, there is also an extra block of text in the description area of the card which details that you can exert a character (turning them sideways and opening them to attack) of a minimum cost in order to play the song card for free
One damage can kill smaller characters or chip away at bigger ones, helping you clear your opponents boards while still bringing in the precious lore you need
It casually dipping into each of the four packs is welcome as, as you might have picked up on earlier, new seasons of cards can be daunting to players (myself included) for the rules they bring
But it's only playable as a one-off in Vintage (and formats that follow the Vintage ban-list, like Canadian Highlander), so we're giving the spot to Gaea's Cradle
Pair it with our pal Maui from above, and you could reuse this card again and again
But, the price is eye-wateringly high