Cheapest priced copy (Double Masters): $69.99 at Card Kingdom, near mint, their price list as of .
Mana Echoes 
Enchantment · Rare · Onslaught · #218
Whenever a creature enters, you may add an amount of {C} equal to the number of creatures you control that share a creature type with it.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $69.99 to $159.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 136 | Mythic | $69.99 | $84.99 |
| Onslaught | 218 | Rare | $74.99 | $159.99 |
| The Zeta Set | 64 | Mythic | — | — |
| The Zeta Set | 185 | Mythic | — | — |
| The Zeta Set | 306 | Mythic | — | — |
3 rulings from Wizards of the Coast
- 7 August 2020The creature entering the battlefield shares a creature type with itself if it has any creature types, so Mana Echoes usually adds at least {C}.
- 7 August 2020Mana Echoes counts the number of creatures that share a type, not how many types they share. For example, if a Human Warrior enters while you control two Humans and two other Human Warriors, you'll add five {C}.
- 7 August 2020The amount of mana to add is determined only as the triggered ability of Mana Echoes resolves. The ability isn't a mana ability; players may respond to it.