Sometimes Polymarket lists several related markets that together cover all possibilities and can't both happen (e.g. separate 'BTC tops $X' tiers), but they aren't formally grouped, so nothing forces their prices to add to 100%. When their YES prices total more than $1, you bet against the whole overpriced set by buying NO on each tier. The edge is the missing 100% constraint across markets that the platform never linked together.
Markets on Polymarket where cross-market mutually-exclusive sum-over-one fade is the natural play: