Reading this, they always talk about the refund they receive from the carrier, not the price you paid.

If you (eg only) buy a £1000 ticket, they may only send £900 to the airline as the rest is their commission or a discounted net fare. If the airline issues a full refund then the TA will get £900 back from the airline which they 100% pass on to you. Some tickets will have an obvious service fee and others have that built into the price.