Cheapest priced copy (The Brothers' War Retro Artifacts): $0.49 at Card Kingdom, near mint, their price list as of .
Foundry Inspector 
Artifact Creature — Construct · 3/2 · Uncommon · The Zeta Set · #346
Artifact spells you cast cost {1} less to cast.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
13 printings · $0.49 to $13.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Retro Artifacts | 16 | Uncommon | $0.49 | $1.49 |
| The Brothers' War Retro Artifacts | 79 | Uncommon | $1.79 | $1.99 |
| The Brothers' War Retro Artifacts | 79z | Uncommon | — | — |
| Commander Masters | 385 | Common | $0.49 | $0.79 |
| Commander Legends | 310 | Common | $0.59 | $0.99 |
| Foundations Commander | 259 | Uncommon | $0.59 | — |
| Kaladesh | 215 | Uncommon | $0.49 | $1.49 |
| Neon Dynasty Commander | 152 | Common | $0.59 | — |
| The List | KLD-215 | Uncommon | $0.59 | — |
| Secret Lair Drop | 2106 | Rare | $12.99 | $13.99 |
| The Zeta Set | 104 | Uncommon | — | — |
| The Zeta Set | 225 | Uncommon | — | — |
| The Zeta Set | 346 | Uncommon | — | — |
2 rulings from Wizards of the Coast
- 20 September 2016Once a player has announced an artifact spell, no player may take actions to try to remove Foundry Inspector from the battlefield before that spell's cost is locked in.
- 20 September 2016If an artifact spell has {X} in its mana cost, choose the value for X first, and then reduce the cost by {1}. For example, an artifact that costs {X} with X chosen as 4 costs {3} to cast if you control Foundry Inspector.