Cheapest priced copy (The Brothers' War Commander): $0.69 at Card Kingdom, near mint, their price list as of .
Metalwork Colossus 
Artifact Creature — Construct · 10/10 · Rare · Kaladesh · #222
This spell costs {X} less to cast, where X is the total mana value of noncreature artifacts you control.
Sacrifice two artifacts: Return this card from your graveyard to your hand.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
8 printings · $0.69 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Commander | 147 | Rare | $0.69 | — |
| Commander Masters | 960 | Rare | $0.79 | — |
| Kaladesh | 222 | Rare | $0.79 | $0.99 |
| Marvel Super Heroes Commander | 204 | Rare | $0.79 | $0.79 |
| Marvel Super Heroes Commander | 442 | Rare | $1.49 | — |
| Kaladesh Promos | 222s | Rare | — | $7.99 |
| Secret Lair Drop | 377 | Rare | $2.79 | $2.79 |
| Secret Lair Drop | 378 | Rare | $3.99 | $2.79 |
5 rulings from Wizards of the Coast
- 20 September 2016If a permanent has {X} in its mana cost, X is considered to be 0.
- 20 September 2016Metalwork Colossus's last ability can be activated only if it is in your graveyard.
- 20 September 2016Once a player has announced that they are casting Metalwork Colossus, no player may take actions to try to change the number of artifacts its controller controls before that spell's cost is locked in.
- 20 September 2016The total cost to cast Metalwork Colossus is locked in before you pay that cost. For example, if you control three noncreature artifacts each with mana value 2, including one you can sacrifice to add {C} , the total cost of Metalwork Colossus is {5}. Then you can sacrifice the artifact when you activate mana abilities just before paying the cost.
- 20 September 2016If the total mana value of noncreature artifacts you control is 11 or greater, Metalwork Colossus costs {0} to cast.