Used to be a seed corn by the name of "Fielder's Choice" Mail order type of stuff. Good friend and neighbor bought it. All he could talk about all year was how cheap his seed bill was. I harvested his corn and mine. His yield was 30 BPA lower on the same or even better ground. HE went back to more normal seed the next year and out yielded my corn.
So I would just keep on reading by these type of ads.