When Teemo Strategist deals 3 damage to a unit with Deflect, does the controller pay 1 mana for Deflect or 3 mana (once per damage)?

Ruling: Deflect is paid once. There is only one instance of targeting, so you pay the Deflect cost one time regardless of how much damage is dealt.

Sequence:

• Target the unit with Deflect
• Pay for Deflect once
• Resolve the ability (reveal cards and deal damage based on revealed cards)

Nuances:

• The wording on Teemo Strategist may make it seem like you pay per damage, but you only pay once per targeting instance
• If there is no "do this:" clause on the card, you pick the target and pay for Deflect before resolution