Cheapest priced copy (Innistrad: Double Feature): $0.49 at Card Kingdom, near mint, their price list as of .
Lantern Flare 
Instant · Rare · Innistrad: Crimson Vow · #351
Cleave {X}{R}{W} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Lantern Flare deals X damage to target creature or planeswalker and you gain X life. [X is the number of creatures you control.]
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.49 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 290 | Rare | $0.49 | $0.49 |
| Innistrad: Crimson Vow Promos | 23s | Rare | — | $0.49 |
| Innistrad: Crimson Vow | 23 | Rare | $0.49 | $0.49 |
| Innistrad: Crimson Vow | 351 | Rare | $0.79 | $0.79 |
5 rulings from Wizards of the Coast
- 19 November 2021You can't cast a spell for both its cleave cost and another alternative cost. For example, if an effect gives an Alchemist's Retrieval in your graveyard a flashback cost of {U}, you can't cast it from your graveyard for its cleave cost.
- 19 November 2021If you cast a spell for its cleave cost, that spell doesn't have any of the text in square brackets while it's on the stack.
- 19 November 2021If you're paying the cleave cost, you choose the value of X.
- 19 November 2021A cleave cost is an alternative cost that's paid instead of the spell's mana cost. Casting a spell for its cleave cost doesn't change the spell's mana value.
- 19 November 2021If an effect allows you to “cast a spell without paying its mana cost,” you can't cast that spell for its cleave cost.