You need to define rawColumns :
public function getProductDatatable()
{
$Product = Product::query();
return Datatables::eloquent($Product)
->addColumn('action', function($row) {
return '<a href="/product/'. $row->id .'/edit" class="btn btn-primary">Edit</a>';
})
->addColumn('add_price', function($row) {
return '<a href="/product/'. $row->id .'/create-price" class="btn btn-primary">Add Price</a>';
})
->rawColumns(['add_price', 'action'])
->make(true);
}