Why is EF4 Code First so slow when storing objects?

I'm currently doing some research on usage of db4o a storage for my web application. I'm quite happy how easy db4o works. So when I read about the Code First approach I kinda liked is, because the way of working with EF4 Code First is quite similar to working with db4o: create your domain objects (POCO's), throw them at db4o, and never look back.

But when I did a performance comparison, EF 4 was horribly slow. And I couldn't figure out why.

I use the following entities :

public class Recipe
    {
     private List _RecipePreparations;
     public int ID { get; set; }
     public String Name { get; set; }
     public String Description { get; set; }
     public List Tags { get; set; }
     public ICollection Preparations 
               { get { return  _RecipePreparations.AsReadOnly(); } }

    public void AddPreparation(RecipePreparation preparation) 
    {
        this._RecipePreparations.Add(preparation);
    }
}


public class RecipePreparation
    {
        public String Name { get; set; }
        public String Description { get; set; }
        public int Rating { get; set; }
        public List Steps { get; set; }
        public List Tags { get; set; }
        public int ID { get; set; }
    }

To test the performance I new up a recipe, and add 50.000 RecipePrepations. Then I stored the object in db4o like so :

IObjectContainer db = Db4oEmbedded.OpenFile(Db4oEmbedded.NewConfiguration(), @"RecipeDB.db4o");
db.Store(recipe1);
db.Close();

This takes around 13.000 (ms)

I store the stuff with EF4 in SQL Server 2008 (Express, locally) like this :

cookRecipes.Recipes.Add(recipe1);
cookRecipes.SaveChanges();

And that takes 200.000 (ms)

Now how on earth is db4o 15(!!!) times faster that EF4/SQL? Am I missing a secret turbo button for EF4? I even think that db4o could be made faster