Cheapest priced copy (Mirrodin): $0.35 at Card Kingdom, near mint, their price list as of .
Forge Armor 
Instant · Uncommon · Mirrodin · #92
As an additional cost to cast this spell, sacrifice an artifact.
Put X +1/+1 counters on target creature, where X is the sacrificed artifact's mana value.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mirrodin | 92 | Uncommon | $0.35 | $0.49 |