Cheapest priced copy (Innistrad Remastered): $0.35 at Card Kingdom, near mint, their price list as of .
Ghoultree 
Creature — Zombie Treefolk · 10/10 · Rare · Dark Ascension · #115
This spell costs {1} less to cast for each creature card in your graveyard.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dark Ascension | 115 | Rare | $0.49 | $0.79 |
| Innistrad Remastered | 198 | Uncommon | $0.39 | $0.49 |
| Innistrad Remastered | 411 | Uncommon | $0.35 | $1.49 |
2 rulings from Wizards of the Coast
- 24 January 2025Ghoultree’s ability can’t reduce the total cost to cast the spell below {G}.
- 24 January 2025Once you begin to cast Ghoultree, no player may take actions until you’re done. Notably, opponents can’t try to remove creature cards from your graveyard to change Ghoultree’s cost.