On the other hand, video cards meant for games generally can't take sustained load. By that I mean you can't run them at 90-100% load for days on end in e.g. a

On the other hand, video cards meant for games generally can't take sustained load. By that I mean you can't run them at 90-100% load for days on end in e.g. a render farm, they invariably melt. You're paying for better build quality and for having enough money for a render farm.