When you attempt to activate an altar, as in the "Hold the Line" quest in Altar of Despair, is it necessary for the hero to pay 250 coin each round to gain the use of the power of the altar?

" Good Altars: To activate a good altar, a hero must stand on top of the altar, spend 2 movement points as a movement action, and spend 250 coins. The altar’s effect then takes place as described in the quest."

It costs 250 coins and 2 movement points each time you want to activate the altar. I don't have the quest in front of me, so if it says something like "if a hero activates an altar, then X happens once per round for the rest of the quest", then they only need to pay once; however, I seem to recall it just says something happens immediately when the altar is activated, in which case the heroes need to pay for each use (and could theoretically use it multiple times in a single round, unless the quest rules forbid it).