Cheapest priced copy (Bloomburrow Promos): $5.99 at Card Kingdom, near mint, their price list as of .
Mockingbird 
Creature — Bird Bard · 1/1 · Rare · Bloomburrow · #305
Flying
You may have this creature enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast this creature, except it's a Bird in addition to its other types and it has flying.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
4 printings · $5.99 to $27.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Bloomburrow | 61 | Rare | $6.49 | $6.99 |
| Bloomburrow | 305 | Rare | $8.99 | $27.99 |
| Bloomburrow Promos | 61p | Rare | $5.99 | $10.99 |
| Bloomburrow Promos | 61s | Rare | — | $13.99 |
7 rulings from Wizards of the Coast
- 26 July 2024If the copied creature has {X} in its mana cost, X is 0.
- 26 July 2024You can choose not to have Mockingbird enter as a copy of another creature. If you do, it will just be a 1/1 Bird Bard creature with flying, an ability that didn’t do anything, and the opportunity for a good self-deprecating joke or two.
- 26 July 2024If the copied creature is copying something else, then Mockingbird enters as whatever that creature copied, with the noted exceptions.
- 26 July 2024Mockingbird copies exactly what was printed on the original creature, except it’s a Bird in addition to its other types and it has flying, and nothing else (unless that creature is copying something else or is a token; see below). It doesn’t copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.
- 26 July 2024If the copied creature is a token, Mockingbird copies the original characteristics of that token as stated by the effect that created that token, with the noted exceptions.
- 26 July 2024Any “enters” abilities of the copied creature will trigger when Mockingbird enters. Any “as [this creature] enters” or “[this creature] enters with” abilities of the copied creature will also work.
- 26 July 2024Mockingbird’s second ability counts all mana spent to cast Mockingbird, not just mana spent on {X}. If there are any additional costs to cast it, the mana spent to pay those costs counts as well.