Sum price of one to many relation ship (laravel)

i have problem with one to many relation ship! So im try to sum product prices so here is what i mean:

Model: Product.php

/**
* @return IlluminateDatabaseEloquentRelationsHasMany
*/
public function orders(){
    return $this->hasMany(Order::class);
}

Model: Orders.php

/**
* @return IlluminateDatabaseEloquentRelationsHasMany
*/
public function product(){
    return $this->belongsTo(Product::class);
}

So i want make smth like this: $var->product->price->sum();

My database if it needed:

Orders: id product_id|user_id| |-|----------|-------| |1|1 |1 | | | | |

And Products have only 4 columns: id,name,price,description

I mean that:

 products:

  id1

  nameproductname

  price 1.00USD

  id2

  nameproductname2

  price 1.00USD

It must return sum of all product so it must return 2.00USD

@Jonas Staudenmeir

Answer

Using eloquent models without DB

Product::with(['orders' => function($query){
   $query->sum('price');
}])->get();