Cheapest priced copy (Urza's Destiny): $0.35 at Card Kingdom, near mint, their price list as of .
Mental Discipline 
Enchantment · Common · Urza's Destiny · #37
{1}{U}, Discard a card: Draw a card.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
1 printing · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Urza's Destiny | 37 | Common | $0.35 | $0.79 |