Cheapest priced copy (Secrets of Strixhaven Commander): $1.49 at Card Kingdom, near mint, their price list as of .
Thunderclap Drake 
Creature — Drake · 2/1 · Rare · Secrets of Strixhaven Commander · #204
Flying
Instant and sorcery spells you cast cost {1} less to cast.
{2}{U}, Sacrifice this creature: When you next cast an instant or sorcery spell this turn, copy it for each time you've cast your commander from the command zone this game. You may choose new targets for the copies.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $1.49 to $2.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Outlaws of Thunder Junction Commander | 17 | Rare | $1.99 | — |
| Outlaws of Thunder Junction Commander | 53 | Rare | $2.79 | — |
| Secrets of Strixhaven Commander | 204 | Rare | $1.49 | — |
9 rulings from Wizards of the Coast
- 12 April 2024The copies made by Thunderclap Drake's delayed triggered ability are created on the stack, so they're not "cast."
- 12 April 2024If a spell that's copied has an X whose value was determined as it was cast, the copies will have the same value of X.
- 12 April 2024If the spell that's copied divides damage or distributes counters among a number of targets, the division and number of targets can't be changed.
- 12 April 2024You can't choose to pay any additional costs for the copies. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copies too.
- 12 April 2024If you have multiple commanders, you'll copy the next instant or sorcery spell you cast this turn for each time you've cast either of them. For example, if you've cast one commander once and one twice, you'll copy that spell three times.
- 12 April 2024Thunderclap Drake's second ability can't reduce the amount of colored mana you pay for a spell. It reduces only the generic mana component of that spell's cost.
- 12 April 2024Thunderclap Drake's second ability doesn't change the mana cost or mana value of any spell. It changes only the total cost you pay to cast instant and sorcery spells.
- 12 April 2024If the spell that's copied is modal (that is, it says "Choose one —" or the like), the copies will have the same mode or modes. You can't choose different ones.
- 12 April 2024The last sentence of Thunderclap Drake's rules text was inadvertently omitted from the card. Its Oracle text has been updated to include that sentence.