This gist works in conjunction with https://gist.github.com/joshfeck/52ac749150322a2e4221. You can add the following to /gateways/invoice/template.php to display the price without surcharge and surcharge amount as line items on the invoice.

add-to-template.php

// suggested code placement is right after the line that says:
// $pdf->ImprovedTable($header, $attendees, $w, $alling);

$pdf->Ln(1);
$pdf->my_itemised_surcharge($registration_ids, $attendees);