Cheapest priced copy (Commander Legends: Battle for Baldur's Gate): $0.35 at Card Kingdom, near mint, their price list as of .
Draconic Lore 
Instant · Common · Tarkir: Dragonstorm Commander · #151
This spell costs {2} less to cast if you control a Dragon.
Draw three cards.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends: Battle for Baldur's Gate | 64 | Common | $0.35 | $0.49 |
| Tarkir: Dragonstorm Commander | 151 | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 10 June 2022The cost of Draconic Lore is determined and locked in as you cast it before any mana abilities are activated and before any player can respond. Notably, this means that no player can respond to remove your Dragon before the cost is reduced, and if you sacrifice that Dragon as part of a mana ability, the cost won't be increased.