Such a diet exists. It's called eating less meat and sugar.
And don't get me started on only unhealthy junk being cheap. Not only have all fast food chains hiked up their prices to near uncompetitive levels, but even fruit and veggies are dirt cheap in America. Europeans pay far more, especially when comparing PPP, than Americans, when it comes to healthy eating. Yet they manage.
Meat is just so calorie dense that even switching to carbs is a massive upgrade.
The carbs they talk about are simple carbs, with high glycemic indexes. Something like whole wheat is going to be a lot healthier for your health than white rice.
Meat may also promote consumption of alcohol, which isn't great for weight loss.