Cheapest priced copy (Fallout): $1.99 at Card Kingdom, near mint, their price list as of .
Strong Back 
Enchantment — Aura · Rare · Fallout · #83
Enchant creature
Equip abilities you activate that target enchanted creature cost {3} less to activate.
Aura spells you cast that target enchanted creature cost {3} less to cast.
Enchanted creature gets +2/+2 for each Aura and Equipment attached to it.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $1.99 to $6.99 at Card Kingdom
3 rulings from Wizards of the Coast
- 8 March 2024Strong Back’s third ability won’t reduce its own cost.
- 8 March 2024Strong Back’s abilities reduce only the amount of generic mana in equip abilities that target the enchanted creature and in the total cost of Aura spells that target the enchanted creature. For example, it will reduce the total cost of Animal Friend from {1}{G} to {G}.
- 8 March 2024Some Equipment creature cards in other sets have reconfigure, a different ability that attaches them to a creature. Reconfigure is not an equip ability, and reconfigure costs are not reduced by Strong Back’s second ability. Equip variants or equip abilities with restrictions, like the “equip Citizen” ability of Ceremonial Groundbreaker from the Streets of New Capenna® set, are still equip abilities, and their costs will be reduced by Strong Back’s second ability.