WP Import Export supports the use of custom PHP functions in all export types for Export Fields.

For regular export fields, you can click on the export field Setting Icon and then use the “Export the value returned by a PHP function” option:

Add Function name of in input field.

open theme’s function.php file or any other file that direct include.

add function that return valid value.

function add_currency_simbol( $value ) {
        return "$ " . $value;
}