Cheapest priced copy (The List): $0.59 at Card Kingdom, near mint, their price list as of .
Game Plan 
Sorcery · Rare · Battlebond · #35
Assist (Another player can pay up to {5} of this spell's cost.)
Each player shuffles their hand and graveyard into their library, then draws seven cards. Exile Game Plan.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.59 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battlebond | 35 | Rare | $0.79 | $6.99 |
| The List | BBD-35 | Rare | $0.59 | — |
4 rulings from Wizards of the Coast
- 8 June 2018You may reveal a card with assist and discuss how to pay for it before you begin to cast the spell. Targets are chosen for that spell before you choose another player to help you pay for it and before that player has committed any mana to doing so.
- 8 June 2018If an effect allows a player to cast a spell spending mana “as though it were mana of any color” or “of any type,” that player must still pay for the colored mana in that spell’s total cost. That cost doesn’t become generic.
- 8 June 2018Only the generic mana portion of a spell’s cost can be paid with assist. Any colored mana costs must be paid by the spell’s controller, even if the assisting player paid mana of that color.
- 8 June 2018Assist allows another player to pay for any amount of generic mana. If an effect changes the cost of the spell, the amount that player may pay will be more or less than the amount in the spell’s reminder text.