Cheapest priced copy (Final Fantasy Commander): $2.29 at Card Kingdom, near mint, their price list as of .
Archaeomancer's Map 
Artifact · Rare · Commander 2021 · #12
When this artifact enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle.
Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
6 printings · $2.29 to $44.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2021 | 12 | Rare | $2.99 | — |
| Commander 2021 | 339 | Rare | $5.99 | — |
| Final Fantasy Commander | 230 | Rare | $2.29 | $5.99 |
| The Lost Caverns of Ixalan Commander | 101 | Rare | $15.99 | $44.99 |
| The List | C21-12 | Rare | $2.99 | — |
| Secrets of Strixhaven Commander | 136 | Rare | $2.49 | — |
One ruling from Wizards of the Coast
- 16 April 2021The last ability triggers only if that opponent controls more lands than you after the land enters the battlefield. The ability will check again as it tries to resolve. If that opponent doesn't still control more lands than you at that time, the ability won't resolve.