Example of how to add an additional 'Ticket Base price' column into the CSV.

tw_ee_csv_add_ticket_base_price.php

<?php

add_filter(
    'FHEE__EventEspressoBatchRequest__JobHandlers__RegistrationsReport__reg_csv_array',
    'tw_ee_csv_add_ticket_base_price',
    20,
    2
);
function tw_ee_csv_add_ticket_base_price(
    array $csv_row,
    $reg_row
) {
	$reg = EEM_Registration::instance()->get_one_by_ID($reg_row['Registration.REG_ID']);
	$ticket = $reg->ticket();
	$ticket_base_price[esc_html__('Ticket Base Price', 'event_espresso')] = $ticket->base_price()->amount();
	$csv_row = EEH_Array::insert_into_array(
        $csv_row,
        $ticket_base_price,
        'Ticket Name',
        false
    );
    return $csv_row;
}