Cheapest priced copy (New Phyrexia): $2.79 at Card Kingdom, near mint, their price list as of .
Mutagenic Growth 
Instant · Common · The List · #NPH-116
({G/P} can be paid with either {G} or 2 life.)
Target creature gets +2/+2 until end of turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
3 printings · $2.79 to $22.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Masters 2015 | 149 | Uncommon | $2.99 | $11.99 |
| New Phyrexia | 116 | Common | $2.79 | $22.99 |
| The List | NPH-116 | Common | $3.49 | — |
5 rulings from Wizards of the Coast
- 1 June 2011As you cast a spell or activate an activated ability with one or more Phyrexian mana symbols in its cost, you choose how to pay for each Phyrexian mana symbol at the same time you would choose modes or choose a value for X.
- 1 June 2011To calculate the mana value of a card with Phyrexian mana symbols in its cost, count each Phyrexian mana symbol as 1.
- 1 June 2011Phyrexian mana is not a new color. Players can't produce Phyrexian mana.
- 1 June 2011If you're at 1 life or less, you can't pay 2 life.
- 1 June 2011A card with Phyrexian mana symbols in its mana cost is each color that appears in that mana cost, regardless of how that cost may have been paid.