Cheapest priced copy (Kaladesh): $0.49 at Card Kingdom, near mint, their price list as of .
Toolcraft Exemplar 
Creature — Dwarf Artificer · 1/1 · Rare · Kaladesh · #32
At the beginning of combat on your turn, if you control an artifact, this creature gets +2/+1 until end of turn. If you control three or more artifacts, it also gains first strike until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Kaladesh | 32 | Rare | $0.49 | $0.99 |
| Kaladesh Promos | 32s | Rare | — | $1.49 |
2 rulings from Wizards of the Coast
- 20 September 2016Whether or not you control three or more artifacts is checked only as the triggered ability resolves.
- 20 September 2016If you control no artifacts as your combat phase begins, Toolcraft Exemplar's triggered ability doesn't trigger at all. If you control no artifacts as the triggered ability resolves, it has no effect.