Choosing between Yes and No isn't only a question of whether the event will happen. It's a question of whether the current price is wrong, and in which direction.
Say Yes is trading at 60¢. A trader who reads the real probability as closer to 75% sees Yes as underpriced. A trader who reads it as closer to 40% sees the same contract as overpriced and looks at No instead. Both views can pay off, because both are positions on the price rather than on the event alone. Neither is a recommendation — which price is right is precisely what the market is arguing about.
How price affects risk and reward
A high-priced contract costs more and pays less if it turns out to be correct. A low-priced contract costs less and pays more, because the market considers the outcome unlikely.
Yes at 80¢: costs 80¢, returns 20¢ per contract if correct. The market already prices in a high probability, so the upside is limited.
Yes at 20¢: costs 20¢, returns 80¢ per contract if correct, but the market gives it only a 20% chance.
Neither is inherently the better trade. What matters is whether the market's estimate is accurate. A 20¢ contract looks cheap, but the low price is the market's estimate of the odds, not a discount on them.
Closing early
You can close any position before the market resolves. If the price has moved in your favor, closing locks in a gain. If it's moved against you, closing limits your loss rather than waiting to see whether you're right at resolution.