Yes, if you were time constrained, the additional TPs and Avios is worth about £100 to £150 in terms of alternative arrangements to give similar extra TPs and Avios. Then I guess you add a bit for the seat and food.

If the overnight return was nearer £300 it may be more interesting, otherwise it's a relatively cheap way to get into CW, globally, accepting that the distance to/from Accra is shorter than even Boston.