Cheapest priced copy (Commander Masters): $0.99 at Card Kingdom, near mint, their price list as of .
Efficient Construction 
Enchantment · Uncommon · Commander Masters · #88
Whenever you cast an artifact spell, create a 1/1 colorless Thopter artifact creature token with flying.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.99 to $4.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Aether Revolt | 33 | Uncommon | $1.49 | $4.49 |
| Commander Masters | 88 | Uncommon | $0.99 | $1.99 |
One ruling from Wizards of the Coast
- 9 February 2017Efficient Construction’s triggered ability resolves before the spell that caused it to trigger. The ability will resolve even if that spell is countered.