Cheapest priced copy (Commander 2020): $0.35 at Card Kingdom, near mint, their price list as of .
Spirit Cairn 
Enchantment · Uncommon · Commander 2020 · #100
Whenever a player discards a card, you may pay {W}. If you do, create a 1/1 white Spirit creature token with flying.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2020 | 100 | Uncommon | $0.35 | — |
| Judgment | 26 | Uncommon | $0.35 | $0.79 |
| Ultimate Masters | 37 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 7 December 2018If a player discards a card during their cleanup step due to having too many cards in hand, any appropriate abilities that trigger on discarding that card (such as Spirit Cairn’s ability) trigger. If this happens, those triggered abilities are put onto the stack and players receive priority in that cleanup step to cast spells or activate abilities (normally, no players may take actions during a cleanup step). Another cleanup step is created following that one.
- 7 December 2018You can’t pay {W} multiple times to create more than one token each time you resolve Spirit Cairn’s triggered ability.