But he wants to book it thru amex travel
Sorry, if I was unclear, you can book a business class ticket on El Al via Amex travel and then request a refund via voucher and still get the 35% from Amex. If he then uses the voucher on elal.com he will get the full value utilized. If he goes to a travel agent they will probably charge an extra fee as they do not earn commission, if you pay via a voucher