Cheapest priced copy (Commander Legends): $0.39 at Card Kingdom, near mint, their price list as of .
On Serra's Wings 
Legendary Enchantment — Aura · Uncommon · Dominaria · #28
Enchant creature
Enchanted creature is legendary, gets +1/+1, and has flying, vigilance, and lifelink.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.39 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends | 380 | Uncommon | $0.39 | — |
| Dominaria | 28 | Uncommon | $0.49 | $2.99 |
| The List | DOM-28 | Uncommon | $0.49 | — |
3 rulings from Wizards of the Coast
- 27 April 2018If you control two permanents with the same name but only one is legendary, the "legend rule" doesn't apply.
- 27 April 2018If you control two On Serra's Wings attached to two creatures you control with the same name, the "legend rule" applies to the enchanted creatures and to On Serra's Wings at once. You can choose to keep the On Serra's Wings that enchants the creature you wish to keep.
- 27 April 2018Multiple instances of flying, vigilance, and/or lifelink on the same creature are redundant.