Cheapest priced copy (Mirrodin): $0.35 at Card Kingdom, near mint, their price list as of .
Steel Wall 
Artifact Creature — Wall · 0/4 · Common · Duel Decks: Elspeth vs. Tezzeret · #41
Defender (This creature can't attack.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Elspeth vs. Tezzeret | 41 | Common | $1.49 | — |
| Mirrodin | 248 | Common | $0.35 | $3.49 |