You are not passing anything to the view but an empty object, hence why it is saying model.price is null. If you want your editor template to be populated you must say
public ActionResult Create()
{
ProductItems items = new ProductItems();
items.Price = 15.99;
return View(items);
}
Since you are passing the view a model of type ProductItems
your view must also expect that type. You should be putting your Model Classes in to the Models folder. Default values to call in your view would be
@model NameSpace.Models.ProductItems, not sure of the path to your model class.