free option

A promise to trade at a price that stands still is a gift to whoever knows more than you: they take the deal only when the price has gone stale in their favor, and walk past when it hasn't.

Traders call this being picked off. An option is the right, never the duty, to trade at a set price — and a standing buy offer hands that right out for free, to everyone, including the seller who just learned something you haven't. The offer survives only by repricing faster than the news travels. The same shape lives far from markets: any standing rule that never updates is a free option to whoever notices the world has moved first.