PHP - Help With Charge Formula

This code, that I didn't write, but am trying to modify, generates the cost of a video purchase.

One line (line 32) is a formula , I believe for setting a purchase price amount:

$amout += $video->video_play_price?$video->video_play_price:$video_cost;

Another line (line 50) is a formula for deducting to create another amount:

 $uploader_amount = $video_cost - $charge;

I think line 50 is correct except for I don't think $video_cost in the final price, but I'm no expert at reading this code. I tried this without success:

 $uploader_amount = $video_play_price - $charge;

Here is the full code, any help with line 50, will be appreciated.

<?php
if (IS_LOGGED == false) {
    $data = array('status' => 400, 'error' => 'Not logged in');
    echo json_encode($data);
    exit();
}

if (!empty($_POST['id'])) {

    if (!is_array($_POST['id'])) {
        $id_array[] = $_POST['id'];
    } else {
        $id_array = $_POST['id'];
    }

    // get cost video
    $db->where('name', 'video_play_price');
    $db_cost = $db->getOne('config');
    $video_cost = (float)$db_cost->value;

    $count_video = count($id_array);
    $user_id = $user->id;
    $wallet = (float)str_replace(',', '', $user->wallet);


	$amout = 0;
	foreach ($id_array as $id) {
            $video_id = (int)PT_Secure($id);

            // get video data
            $video = $db->where('id', $id)->getOne(T_VIDEOS);
			$amout += $video->video_play_price?$video->video_play_price:$video_cost;

	}

//   $amout = $video_cost * $count_video;

    $charge = ( $video_cost *0.50 );

    if ($wallet >= $amout) {

        $new_wallet = (string)($wallet - $amout);

        $db->startTransaction();

        $inserted_records = 0;
        foreach ($id_array as $id) {
            $video_id = (int)PT_Secure($id);

         $uploader_amount = $video_cost - $charge; 

            // get video data
            $video = $db->where('id', $id)->getOne(T_VIDEOS);


            // add data to paid table
            $insert_buy = $db->insert('u_paid_videos', [
                'id_user' => $user_id,
                'id_video' => $video_id,
                'session_key' => $_SESSION['session_key'],
                'video_play_price' => (string)$video_cost,
                'video_title' => $video->title,
                'user_id_uploaded' => $video->user_id,
                //'up_credit'=>$video_cost,
                'up_credit'=>$uploader_amount,
            ]);

            if ($insert_buy) { $inserted_records++; }
            //add wallet users' video
        $userwallet = $db->where('id', $video->user_id)->getOne(T_USERS);

        //$videouserwallet = $userwallet->wallet+$video_cost;
        $videouserwallet = $userwallet->wallet+$uploader_amount;
        $db->where('id', $video->user_id);
        $update_wallet = $db->update(T_USERS, [
          // 'wallet' => $videouserwallet,
            'wallet' => number_format($videouserwallet, 2, '.', ''),
        ]);
        }

        $db->where('id', $user_id);
        $update_wallet = $db->update(T_USERS, [
            'wallet' => $new_wallet,
        ]);


        if (($inserted_records == $count_video) && $update_wallet) {
            $db->commit();

            echo json_encode([
                'status' => 200
            ]);
            exit();
        } else {
            $db->rollback();

            echo json_encode([
                'status' => 400,
                'error' => 'Buy process error'
            ]);
            exit();
        }

    } else {

        echo json_encode([
            'status' => 400,
            'error_num' => 1,
            'error' => 'Not enough money'
        ]);
        exit();

    }

} else {

    echo json_encode([
        'status' => 400,
        'error' => 'Bad Request, Invalid or missing parameter'
    ]);
    exit();

}