I just did a mileage run that worked out costing 2.5 cents a mile for me and 1.25 cents a mile for my daughter. Using the BA houshold account these miles are pooled.

BA RT to Asia from the US(ORD-LHR-TPE for example which in BA F must be like a 24 hr vacation in and of itself) in F is about $15k, cost to me for the 150K miles needed to cash in a F award on BA is just about $4K because of mileage runs(would be half that if I were BA gold).