Overrun is one of the defining green cards, a little like Death Cloud for black in that you set it up and effectively end the game with it, it is what you get as reach in green creature decks and does very well at ending games promptly
In fact, the only connection to real world money is the redemption of code cards from physical TCG products so you can have those cards and cosmetics in the game, but even those can be acquired digitally with in-game currency without ever having to spend a dime
Farfetchd can be obtained from Eevee Grove pack in the Eevee Grove set
Just think about how easy it will be to find cards that you need for the mere cost of 2 life
Vintage Slabs
At the time of Unfinity 's release, the following card sets are permitted in the Standard format: Innistrad: Midnight Hunt , Innistrad: Crimson Vow , Kamigawa: Neon Dynasty , Streets of New Capenna , and Dominaria United