Does Ezreal reduce the cost of paying Flame Chompers when discarded?

Ruling: No, Ezreal does not reduce the cost of Flame Chompers. Flame Chompers has an optional cost but not an optional additional cost, which is what Ezreal requires.

Nuances:

• Optional additional costs must use both the phrase "as an additional cost" AND the word "may" to qualify for Ezreal's discount
• Flame Chompers uses "you may pay" but lacks the "as an additional cost" phrase
• Flame Chompers is a trigger ability on discard, not a passive ability like true optional additional costs
• The cost itself is optional (you choose whether to play it), but it's not formatted as an "optional additional cost" in the rules sense