Cheapest priced copy (Darksteel): $0.35 at Card Kingdom, near mint, their price list as of .
Arcbound Worker 
Artifact Creature — Construct · 0/0 · Common · Darksteel · #104
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
4 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Elspeth vs. Tezzeret | 40 | Common | $0.39 | — |
| Darksteel | 104 | Common | $0.35 | $1.99 |
| Modern Masters | 201 | Common | $0.39 | $0.49 |
| World Championship Decks 2004 | ap104a | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 25 September 2006If this creature gets enough -1/-1 counters put on it to cause its toughness to be 0 or less (or the damage marked on it to be lethal), modular will put a number of +1/+1 counters on the target artifact creature equal to the number of +1/+1 counters on this creature before it left the battlefield.