Does Ezreal's cost reduction work on Draven's ability that has a 'may pay' cost when attacking or defending?

Ruling: Ezreal's cost reduction does not work on Draven's ability. Ezreal only discounts cards that have "as an additional cost" and "may" wording together, which are optional additional costs paid when playing a card. Draven's ability is a triggered ability with its own cost, not an additional cost to cast.

Nuances:

• The "may" wording on Draven refers to whether you want to pay the cost for the triggered ability to resolve, not an optional additional cost to cast
• Optional additional costs are only paid when you play the card itself, not when using triggered abilities
• Ezreal works with effects like Accelerate that have "as an additional cost" wording