Cheapest priced copy (Wilds of Eldraine: Enchanting Tales): $2.79 at Card Kingdom, near mint, their price list as of .
Leyline of Abundance 
Enchantment · Rare · Core Set 2020 Promos · #179p
If this card is in your opening hand, you may begin the game with it on the battlefield.
Whenever you tap a creature for mana, add an additional {G}.
{6}{G}{G}: Put a +1/+1 counter on each creature you control.
Legal inCommanderModernLegacyVintage
Banned inPioneer
Not legal inBrawlStandardPauper
4 printings · $2.79 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 179 | Rare | $2.99 | $5.99 |
| Core Set 2020 Promos | 179p | Rare | $6.49 | $11.99 |
| Core Set 2020 Promos | 179s | Rare | — | $5.49Out of stock |
| Wilds of Eldraine: Enchanting Tales | 56 | Rare | $2.79 | $4.99 |
2 rulings from Wizards of the Coast
- 12 July 2019An ability that triggers "whenever you tap a creature for mana" triggers only if you activate a mana ability of a creature including {T} in its cost. Mana abilities that don't include the {T} symbol and instead say "Tap an untapped creature you control" or similar won't cause Leyline of Abundance's second ability to trigger. Similarly, it won't trigger if you tap a creature to activate a mana ability of another object (even if that mana ability also includes {T}).
- 19 March 2021A player's "opening hand" is the hand of cards the player has after all players have taken mulligans. If players have any cards in hand that allow actions to be taken with them from a player's opening hand, the starting player takes all such actions first in any order, followed by each other player in turn order. Then the first turn begins.