That is not correct, but you're partially right.
You must deduct what is deemed to be a personal benefit. So you're quite right, if there was a meal, if there was some hard benefit--a briefcase, a bag, a book, or what have you--those things would have to be calculated and prorated. But the other hard costs, as you call them, of the convention, such as the stage, the lights, the mikes, the books, the delegate guides, and the rental of the hall are not considered a personal benefit. In fact, we have a mountain of legal advice as well as interpretations from CRA that say that we must receipt convention contributions. We do not have a choice about receipting convention contributions, and they are considered to be a monetary contribution to a political party for the purposes of the Elections Act.