Can You Pay for Bargain on a Free Spell
For example if you entered "Venusaur" into the search box, you'd get a nice list of all the Venusaur cards from each of the TCG sets
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of this ability)
While theres certainly no requirement, playing a commander like Vrondiss, Rage of Ancients or Wyll, Blade of Frontiers (alongside a green background) makes this even more enticing
The Witherbloom Pestilence deck is worth $63.52 according to TCGPlayer
Flare of Duplication Flare of Duplication Modern Horizons 3, Rare Yeesh