Auto for sale content

/**
 * Set Content for Sale
 * If a post has tags that starts with a dollar sign, the post
 * will be automatically set for sale, allowing users to purchase
 * access to the post with myCRED Points.
 * Multiple tags can be used in which case their value is added up.
 * @requires myCRED 1.4 or higher
 * @version 1.1
 */
add_action( 'save_post', 'mycred_pro_set_content_for_sale' );
function mycred_pro_set_content_for_sale( $post_id ) {
    // If autosave
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;
    // If myCRED is disabled
    if ( ! function_exists( 'mycred' ) ) return;
    // If draft posts
    if ( get_post_status( $post_id ) == 'draft' ) return;

    // Get post tags
    $tags = wp_get_post_tags( $post_id );
    if ( ! empty( $tags ) ) {

        // Check for price tags
        $price_tags = array();
        foreach ( $tags as $tag ) {
            if ( substr( $tag->name, 0, 1 ) == '$' )
                $price_tags[] = $tag->name;
        }

        // Load myCRED
        $mycred = mycred();

        // Prep cost
        $cost = 0;

        // If we found price tags
        if ( ! empty( $price_tags ) ) {

            // Add them up in case there is more then one
            foreach ( $price_tags as $tag ) {
                $price = ltrim( $tag, '$' );
                $cost = $mycred->number( $cost+$price );
            }

        }

        // If price is higher then zero
        if ( $cost > 0 ) {

            // Sell Content preference must be setup for myCRED to allow purchases
            if ( ! isset( $mycred->sell_content['defaults']['expire'] ) )
                $mycred->sell_content['defaults']['expire'] = 0;

            $sales_data = array(
                'status'       => 'enabled',
                'price'        => $cost,
                'button_label' => $mycred->sell_content['defaults']['button_label'],
                'expire'       => $mycred->sell_content['defaults']['expire']
            );

            // Save
            update_post_meta( $post_id, 'myCRED_sell_content', $sales_data );
        }
    }
}