If there's no intent to sell the "halo" cars, why even bother building them at all? That development money could be better spent toward making better competition for the markets that they do choose to compete in. The "GT500s sell Focuses" mindset is outdated thinking.
Ford didn't create the Ford Performance Vehicles branch for nothing. It would be highly wasteful just to use it as [just] a marketing ploy. They have the division. They might as well stock it with a full cache of vehicles. If they made the GT500 and GT350 together, they'd still be able to sell every last one. Questioning that would be not much different than asking why they make the Focus ST and the Focus RS at the same time.
Ford didn't create the Ford Performance Vehicles branch for nothing. It would be highly wasteful just to use it as [just] a marketing ploy. They have the division. They might as well stock it with a full cache of vehicles. If they made the GT500 and GT350 together, they'd still be able to sell every last one. Questioning that would be not much different than asking why they make the Focus ST and the Focus RS at the same time.