Cheapest priced copy (Fallen Empires): $0.35 at Card Kingdom, near mint, their price list as of .
Tidal Flats 
Enchantment · Common · Fallen Empires · #27b
{U}{U}: For each attacking creature without flying, its controller may pay {1}. If that player doesn't, creatures you control blocking that creature gain first strike until end of turn.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Fallen Empires | 27a | Common | $0.35 | — |
| Fallen Empires | 27b | Common | $0.35 | — |
| Fallen Empires | 27c | Common | $0.35 | — |
3 rulings from Wizards of the Coast
- 4 October 2004Can be used more than once in a turn. Each time, the opponent can pay to prevent giving first strike to a creature, but this payment only stops the current activation and not future activations of Tidal Flats.
- 4 October 2004First Strike is granted to your creatures currently blocking non-Flyers when this effect resolves.
- 4 October 2004The payment is made when the Tidal Flats effect resolves.