No, you said it yourself: it's an ability, which is different from a spell. If you get a discount on creature spells, it won't affect abilities.
111.1. A spell is a card on the stack. As the first step of being cast (see rule 601, "Casting Spells"), the card becomes a spell and is moved to the top of the stack from the zone it was in, which is usually its owner's hand. (See rule 405, "Stack.")
112.1a An ability can be a characteristic an object has that lets it affect the game. An object's abilities are defined by its rules text or by the effect that created it. Abilities can also be granted to objects by rules or effects. (Effects that grant abilities usually use the words "has," "have," "gains," or "gain.") Abilities generate effects. (See rule 609, "Effects.")
112.1c An ability can be an activated or triggered ability on the stack. This kind of ability is an object. (See section 6, "Spells, Abilities, and Effects.")
- Activating Activated Abilities
602.1. Activated abilities have a cost and an effect. They are written as "[Cost]: [Effect.] [Activation instructions (if any).]"