calculated-fields.php

<?php
add_filter( 'jet-engine/listings/allowed-callbacks', 'jet_he_add_calc_callback', 10, 2 );
function jet_he_add_calc_callback( $callbacks ) {
	$callbacks['jet_he_calc_fileds']             = 'Calculated total price';
	$callbacks['jet_he_calc_fileds_no_discount'] = 'Calculated total price (without discount)';
	return $callbacks;
}

function jet_he_calc_fileds( $field_1_value ) {
	$license_fee = absint( get_post_meta( get_the_ID(), 'license-fee', true ) );
	$discount    = absint( get_post_meta( get_the_ID(), 'discount', true ) );
	return $field_1_value + $license_fee - $discount;
}

function jet_he_calc_fileds_no_discount( $field_1_value ) {
	$license_fee = absint( get_post_meta( get_the_ID(), 'license-fee', true ) );
	return $field_1_value + $license_fee;
}