Cheapest priced copy (Conspiracy: Take the Crown): $0.49 at Card Kingdom, near mint, their price list as of .
Hedron Matrix 
Artifact — Equipment · Rare · Rise of the Eldrazi · #218
Equipped creature gets +X/+X, where X is its mana value.
Equip {4}
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Conspiracy: Take the Crown | 209 | Rare | $0.49 | $1.49 |
| Rise of the Eldrazi | 218 | Rare | $0.49 | $0.99 |