Cheapest priced copy (Dragons of Tarkir): $0.35 at Card Kingdom, near mint, their price list as of .
Volcanic Rush 
Instant · Common · Dragons of Tarkir · #166
Attacking creatures get +2/+0 and gain trample until end of turn.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragons of Tarkir | 166 | Common | $0.35 | $0.49 |
| The List | DTK-166 | Common | $0.35 | — |
3 rulings from Wizards of the Coast
- 25 February 2015Even though Volcanic Rush affects only attacking creatures, the bonus will remain for the rest of the turn.
- 25 February 2015Only creatures that are attacking as Volcanic Rush resolves will receive the bonus. In other words, casting it before you declare attackers usually won’t do anything.
- 25 February 2015An “attacking creature” is one that has been declared as an attacker that combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step, even if the player it was attacking has left the game, or the planeswalker it was attacking has left the battlefield.