Tenacious Tomeseeker

• WOTC Official Reminder Textofficial rules
  Bargain — You may sacrifice an artifact, enchantment, or token as you cast this spell.

• WWizards of the Coast2023-09-01
  Official Ruling
  If you copy a bargained spell, the copy is also bargained. If a card or token enters the battlefield as a copy of a permanent that’s already on the battlefield, the new permanent isn’t bargained, even if the original was.
• WWizards of the Coast2023-09-01
  Official Ruling
  Adventurer cards aren't instant or sorcery cards while they're in your graveyard. You can't use Tenacious Tomeseeker's ability to return an adventurer card from your graveyard to your hand.
• WWizards of the Coast2023-09-01
  Official Ruling
  Some instant and sorcery spells require additional targets if they’re bargained. You ignore those targeting requirements if those spells aren’t bargained, and you can’t bargain those spells unless you can choose the appropriate targets. On the other hand, you can bargain a permanent spell even if you won’t be able to choose targets for an enters-the-battlefield ability of that permanent once the spell resolves.
• WWizards of the Coast2023-09-01
  Official Ruling
  Bargain represents an optional additional cost. A spell cast with that additional cost paid is “bargained.”
• WWizards of the Coast2023-09-01
  Official Ruling
  Bargain means “As an additional cost to cast this spell, you may sacrifice an artifact, enchantment, or token.”
• WWizards of the Coast2023-09-01
  Official Ruling
  You may sacrifice only one artifact, enchantment, or token to pay a spell’s bargain cost.

Rulings via Scryfall