do you need pay deflect cost twice if you repeat a card

Yes, if you use Repeat to target a unit with Deflect twice, you must pay the Deflect cost twice.

According to Rule 735.1.c, Deflect is an additional cost applied "for each time they choose me."

When you pay a Repeat cost, you execute the spell's instructions an additional time. Rule 746.2 states that choices for the additional execution (such as targets) must be made during the "Make Relevant Choices" step of playing the card. If you choose the same unit with Deflect for both the initial execution and the repeated execution, you have "chosen" that unit twice.

Key Points:

• Mandatory Cost: Deflect is a mandatory additional cost that must be paid when the spell is played (Rule 353.2.a.2).
• Multiple Choices: Because the spell "chooses" the target for each instance of its effect, the Deflect cost triggers for every individual instance of targeting.
• Official Ruling: This is confirmed by official FAQs regarding multi-target spells (like Starfall or Icathian Rain), which clarify that you must pay the Deflect cost for each time the unit is chosen/targeted by the spell, not just once per card played.