Does Lady of Luminosity, Lux trigger when you play a spell with printed cost 5 or more, or does it check the modified cost after reductions (e.g., from Eager Apprentice)?

Ruling: Cost always refers to the printed cost in the upper left corner of the card, not the modified cost after reductions or increases.

Nuances:

• When a card refers to "cost," it means the printed cost as defined in the comprehensive rules
• Cost reductions from effects like Eager Apprentice do not change what cost a spell is considered for trigger purposes