Presumably they think they can sustain the pricing because of consumer inertia. Personally I'd book the cheaper fare from another supplier; BA may be expensive, and be playing games with surcharges, but there are still a lot of cheap ways to fly. I just booked a round the world for around £800 on a mixture of low cost carriers.

Incidentally, there are much better BA/OW Y fares available ex Germany (~£249) just now, and probably from other start points.