Cheapest priced copy (Journey into Nyx): $0.49 at Card Kingdom, near mint, their price list as of .
Battlefield Thaumaturge 
Creature — Human Wizard · 2/1 · Rare · Journey into Nyx · #31
Each instant and sorcery spell you cast costs {1} less to cast for each creature it targets.
Heroic — Whenever you cast a spell that targets this creature, this creature gains hexproof until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.49 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Journey into Nyx | 31 | Rare | $0.49 | $0.99 |
7 rulings from Wizards of the Coast
- 26 April 2014The cost reduction is {1} per target creature, even if the spell targets a creature more than once.
- 26 April 2014Heroic abilities won't trigger when a copy of a spell is created on the stack or when a spell's targets are changed to include a creature with a heroic ability.
- 26 April 2014To calculate the total cost of an instant or sorcery spell you're casting, start with the mana cost (or alternative cost, if applicable), add all cost increases (including additional costs such as those imposed by strive abilities), then subtract all cost reductions (such as the one created by Battlefield Thaumaturge's first ability).
- 26 April 2014Heroic abilities will resolve before the spell that caused them to trigger.
- 26 April 2014The cost reduction created by Battlefield Thaumaturge's first ability can reduce only the generic portion of the spell's total cost. Colored mana requirements aren't affected.
- 26 April 2014Battlefield Thaumaturge's first ability doesn't change that spell's mana cost or mana value. It changes only the amount you actually pay (the “total cost” of the spell).
- 26 April 2014Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.