Cheapest priced copy (Kamigawa: Neon Dynasty): $0.35 at Card Kingdom, near mint, their price list as of .
Boon of Boseiju 
Instant · Uncommon · Kamigawa: Neon Dynasty · #176
Target creature gets +X/+X until end of turn, where X is the greatest mana value among permanents you control. Untap it.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Kamigawa: Neon Dynasty | 176 | Uncommon | $0.35 | $0.79 |
3 rulings from Wizards of the Coast
- 18 February 2022The greatest mana value among permanents you control is determined as Boon of Boseiju resolves.
- 18 February 2022Transforming double-faced permanents, such as those found in this set, have the mana value of their front face at all times, even while back-face-up.
- 18 February 2022If a permanent on the battlefield has {X} in its mana cost, X is 0 when determining that permanent's mana value.