Cheapest priced copy (Streets of New Capenna): $0.35 at Card Kingdom, near mint, their price list as of .
Sewer Crocodile 
Creature — Crocodile · 4/6 · Common · Streets of New Capenna · #60
{3}{U}: This creature can't be blocked this turn. This ability costs {3} less to activate if there are five or more mana values among cards in your graveyard.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Streets of New Capenna | 60 | Common | $0.35 | $0.49 |
6 rulings from Wizards of the Coast
- 29 April 2022The mana value of a double-faced card in your graveyard is always the mana value of the front face.
- 29 April 2022X is 0 when determining the mana value of a card in your graveyard.
- 29 April 2022"Five or more mana values among cards in your graveyard" means there are at least five different mana values among those cards.
- 29 April 2022The mana value of a split card in the graveyard is the total mana value of both halves of that card. It does not have two mana values.
- 29 April 2022The mana value of a land card is 0.
- 29 April 2022Costs to activate an ability are determined only once, before mana abilities are activated. If cards are removed from your graveyard after that point, such as by exiling Jack-o'-Lantern from your graveyard to pay for its mana ability, this won't affect the cost of activating Sewer Crocodile, even if that reduces the number of mana values in your graveyard to below five.