This particular card can be found for anywhere between $20-40, depending on platform, grade, and quality
Being able to turn a creature into two colorless mana can ramp you up exponentially, especially when you have a way to continuously make new token creatures to sacrifice to it
In traditional Magic, or 1v1, you will make your opponent defend and you will attack it
Full Art Supporters are some of the most expensive cards in the game, with the exception of a few rare Charizard cards from 20 years ago
The other day at my local game store I ended a hapless opponent on turn three through his on-curve Thalia
That's a big bump for a creature type, and to have it all in one set means there are plenty of options for using a creature tribe in Standard