You can do that with the keyBy function: https://laravel.com/docs/8.x/collections#method-keyby

$cars =  [
    ['Item' => "Volvo", 'Price' => 22, 'NewPrice' => 18],
    ['Item' => "Volvo", 'Price' => 22, 'NewPrice' => 18.56],
    ['Item' => "BMW",  'Price' => 23, 'NewPrice' => 5.09],
    ['Item' => "Saab",  'Price' => 90, 'NewPrice' => 23],
    ['Item' => "Saab",  'Price' => 90, 'NewPrice' => 24.90],
    ['Item' => "Saab",  'Price' => 90, 'NewPrice' => 13.33],
];

$collection = new \Illuminate\Support\Collection($cars);

$cars = $collection->keyBy('Item');
// Or if you don't want the Item as key of the result.
$cars = $collection->keyBy('Item')->values();