I've tried Kayak and most of its competitors has always found me the lowest price except for last-minute flights where I was forced to use Priceline's name-your

I've tried Kayak and most of its competitors has always found me the lowest price except for last-minute flights where I was forced to use Priceline's name-your-own-price mechanism. These were flights between Thailand-Chicago, Japan-Iowa, Iowa-Houston, and Houston-San Francisco. Maybe Mobissimo works better for European destinations?