Cheapest priced copy (Avatar: The Last Airbender): $0.35 at Card Kingdom, near mint, their price list as of .
Twin Blades 
Artifact — Equipment · Uncommon · Avatar: The Last Airbender · #157
Flash
When this Equipment enters, attach it to target creature you control. That creature gains double strike until end of turn.
Equipped creature gets +1/+1.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Avatar: The Last Airbender | 157 | Uncommon | $0.35 | $0.49 |