Cheapest priced copy (Forgotten Realms Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Hoard-Smelter Dragon 
Creature — Dragon · 5/5 · Rare · Scars of Mirrodin · #93
Flying
{3}{R}: Destroy target artifact. This creature gets +X/+0 until end of turn, where X is that artifact's mana value.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
6 printings · $0.49 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Forgotten Realms Commander | 128 | Rare | $0.49 | — |
| Commander 2014 | 178 | Rare | $0.49 | — |
| Commander 2021 | 173 | Rare | $0.49 | — |
| Commander Anthology Volume II | 104 | Rare | $0.49 | — |
| Starter Commander Decks | 147 | Rare | $0.49 | — |
| Scars of Mirrodin | 93 | Rare | $0.59 | $0.79 |
3 rulings from Wizards of the Coast
- 1 January 2011If the mana cost of a permanent includes {X}, that X is considered to be 0.
- 1 January 2011If the targeted artifact is an illegal target by the time the activated ability resolves, the ability doesn't resolve. Hoard-Smelter Dragon won't get the bonus.
- 1 July 2013If the activated ability resolves but the targeted artifact isn't destroyed (perhaps because it has indestructible or it regenerates), Hoard-Smelter Dragon will still get the bonus.