Cheapest priced copy (Commander Legends: Battle for Baldur's Gate): $4.49 at Card Kingdom, near mint, their price list as of .
Mocking Doppelganger 
Creature — Shapeshifter · 0/0 · Rare · Commander Legends: Battle for Baldur's Gate · #617
Flash
You may have this creature enter as a copy of a creature an opponent controls, except it has "Other creatures with the same name as this creature are goaded." (They attack each combat if able and attack a player other than you if able.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $4.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends: Battle for Baldur's Gate | 617 | Rare | $4.49 | — |
| Commander Legends: Battle for Baldur's Gate | 667 | Rare | $4.49 | — |
6 rulings from Wizards of the Coast
- 10 June 2022Except for the added ability, Mocking Doppelganger copies exactly what was printed on the original creature (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, whether it has any Auras and/or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.
- 10 June 2022If the chosen creature is a token, Mocking Doppelganger copies the original characteristics of that token, except for the added ability. Mocking Doppelganger doesn't become a token in this case.
- 10 June 2022Any enters-the-battlefield abilities of the copied creature will trigger when Mocking Doppelganger enters the battlefield. Any “as [this creature] enters the battlefield” or “[this creature] enters the battlefield with” abilities of the chosen creature will also work.
- 10 June 2022If the chosen creature has {X} in its mana cost, X is considered to be 0.
- 10 June 2022If the chosen creature is copying something else, Mocking Doppelganger will use the copiable values of the chosen creature. In most cases, it will be a copy of whatever the chosen creature is copying.
- 10 June 2022If Mocking Doppelganger somehow enters the battlefield at the same time as another creature an opponent controls, it can't become a copy of that creature. You may choose only a creature that's already on the battlefield.