Learndash - Course price

<?php
/**
 * Return a formatted price of the given course, with currency prefix.
 * It will return 'Free' for courses with no price.
 *
 * @param int $post_id
 * @return string
 */
function bboss_learndash_course_price( $post_id ){
    $options             = get_option( 'sfwd_cpt_options' );
    $currency            = null;

    if ( !is_null( $options ) ) {
        if ( isset( $options[ 'modules' ] ) && isset( $options[ 'modules' ][ 'sfwd-courses_options' ] ) && isset( $options[ 'modules' ][ 'sfwd-courses_options' ][ 'sfwd-courses_paypal_currency' ] ) )
            $currency = $options[ 'modules' ][ 'sfwd-courses_options' ][ 'sfwd-courses_paypal_currency' ];
    }

    if ( is_null( $currency ) ) {
        $currency = 'USD';
    }

    $course_options  = get_post_meta( $post_id, "_sfwd-courses", true );
    $price           = $course_options && isset( $course_options[ 'sfwd-courses_course_price' ] ) ? $course_options[ 'sfwd-courses_course_price' ] : __( 'Free', 'boss-learndash' );

    if ( $price == '' ) {
        $price .= __( 'Free', 'boss-learndash' );
    }

    if ( is_numeric( $price ) ) {
        if ( $currency == 'USD' ) {
            $price = '$' . $price;
        } else {
            $price .= ' ' . $currency;
        }
    }

    return $price;
}