Cheapest priced copy (Foundations Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Valkyrie's Sword 
Artifact — Equipment · Uncommon · Foundations Jumpstart · #276
When this Equipment enters, you may pay {4}{W}. If you do, create a 4/4 white Angel Warrior creature token with flying and vigilance, then attach this Equipment to it.
Equipped creature gets +2/+1.
Equip {3}
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Foundations Jumpstart | 276 | Uncommon | $0.35 | — |
| Kaldheim | 36 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 5 February 2021The Angel Warrior creature token enters the battlefield as a 4/4 creature. Any abilities that trigger when a creature with a certain power or toughness enters the battlefield will see the token enter as a 4/4 creature.
- 5 February 2021You decide whether to pay {4}{W} as the enters-the-battlefield ability resolves. If you do, you immediately create the Angel Warrior creature token and attach Valkyrie's Sword to it. No players may respond to your decision to pay or not, and no player may take actions during this process.