Can you choose not to pay a deflect cost on your own triggered ability to avoid the effect?

Ruling: Yes, you can choose not to pay the deflect cost. When you decline to pay, the ability never goes on the chain in the first place.

Nuances:

• This is not the same as "countering" the ability, since countering would imply the ability went on the chain first
• It's similar to undoing the steps of playing an illegal card - the ability simply doesn't trigger if you don't pay the cost