1. You need 2 joins in order to sort by 'far' related table.
2. You can load it as is and then sort the collection (obviously this one won't scale etc so don't)

So, you could create a scope for this, to make it easier:

// Product model
public function scopeOrderByPrice($query, $order = 'asc')
{
	$relation = $this->variants(); // asuuming variants is relation name
	$related = $relation->getRelated();
	$table = $related->getTable();
	$foreignKey = $relation->getForeignKey();

	$farRelation = $related->price(); // assuming price is relation name
	$farTable = $farRelation->getRelated()->getTable();
	$farForeignKey = $farRelation->getForeignKey();

	$query->join($table, $foreignKey, '=', $this->getQualifiedKeyName())
		->join($farTable, $farForeignKey, '=', $related->getQualifiedKeyName())
		->orderBy($farTable.'.'.'price', $order) // assuming price is column name on prices table
		->select($this->getTable().'.*') // assuming you want only Product properties
		->groupBy($this->getQualifiedKeyName());
}


// then
$products = Product::orderByPrice()->take(10)->get();
//or 
$products = Product::orderByPrice()->paginate(10);

Of course you could hard-code everything in that join if you like:

public function scopeOrderByPrice($query, $order = 'asc')
{
	$query->join('variants', 'variants.product_id', '=', 'products.id')
		->join('prices', 'prices.variant_id', '=', 'variants.id')
		->orderBy('prices.price', $order)
		->select('products.*')
		->groupBy('products.id');
}