Cheapest priced copy (Magic 2015): $0.35 at Card Kingdom, near mint, their price list as of .
Generator Servant 
Creature — Elemental · 2/1 · Common · The List · #M15-143
{T}, Sacrifice this creature: Add {C}{C}. If any of that mana is spent on a creature spell, it gains haste until end of turn. (That creature can attack and {T} as soon as it comes under your control.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
3 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic 2015 | 143 | Common | $0.35 | $1.99 |
| The List | M15-143 | Common | $0.35 | — |
| Ultimate Masters | 133 | Common | $0.35 | $1.49 |
4 rulings from Wizards of the Coast
- 7 December 2018An instant or sorcery spell is not a creature spell, even if that spell creates creature tokens.
- 7 December 2018If the mana is spent on two different creature spells, each of those spells (and resulting creatures) will gain haste until end of turn.
- 7 December 2018If the mana is spent on a noncreature spell that becomes a creature later in the turn, that creature won't have haste.
- 7 December 2018If a creature spell has generic mana only in its alternative or additional cost, the creature will still gain haste.