On most cheap tickets between US/Europe and Israel, the actual ticket price can be 1$. The rest is YQ and airport taxes. Airport taxes can be very high, especially in the UK. IME, most airlines would refund the taxes on non refundable tickets if you ask for it, but they won’t chase after you. Therefore, it will always be worthwhile canceling a ticket you don’t plan on using. It can even work when you book a fake return to get a cheaper OW, and then cancel the way back. Though some LCC’s charge an administration fee for processing a refund which can be more then the actual refund.