British Airways makes a lot of business class award space available, but they’re expensive. Departures from the U.K. incur significant ‘air passenger duty’ and awards also incur fuel surcharges. A roundtrip business class award between the U.S. and U.K. might run $1300 in taxes and fees.
Right now there seems to be a quirk booking awards on British Airways that you can exploit to reduce fuel surcharges (or ‘carrier-imposed surcharges’) by about two-thirds.