Possible Clues:

• Donate twice as much as Gates?
• "Cav/Pag" opera combination, notably
• Event with two headliners, or a description of a restaurant check that includes any of the answers to the starred clues?
• Invoice for a movie stand-in?
• Performance starring two groups, perhaps ... or a theme hint
• Two films shown in succession for the price of one
• Clone tycoon Gates?