In general, when you are asked "What is the probability that the coin came up heads" we interpret this as "how much are you willing to pay for a contract that will be worth 1 dollar if the coin came up heads, and nothing if it came up tails"

Nobody who thinks that the probability is at 75% will buy into the prediction market when the prediction market is at 75%.

A better way to phrase it would be to say: "If you are forced to buy a share in the prediction market, the probability of the event is that probability where you don't care which side of the bet you take."