Cheapest priced copy (The List): $0.59 at Card Kingdom, near mint, their price list as of .
Edgewalker 
Creature — Human Cleric · 2/2 · Uncommon · Scourge · #137
Cleric spells you cast cost {W}{B} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a Cleric spell with mana cost {1}{W}, it costs {1} to cast.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.59 to $17.99 at Card Kingdom
3 rulings from Wizards of the Coast
- 4 October 2004If you have more than one of these on the battlefield, the cost reduction is cumulative.
- 1 August 2008You apply cost reduction effects after other cost modifiers, so it can reduce additional costs or alternative costs if they include {W} and/or {B}.
- 1 August 2008If a spell has hybrid mana symbols in its mana cost, you choose which half you will be paying before determining the total cost. If you choose to pay such a cost with {W} or {B}, Edgewalker can reduce that part of the cost.