M/B is nearly the most expensive economy band - second only to full fat Y, and that attracts 20 TPs on shorthaul. O on the other hand is one of the lowest fare bandings. It's entirely possible to construct this sort of fare so the TP award looks about right. When there are 4 fares involved here (or possibly 2 fares and 2 add-ons) then it's tricky to spot a super expensive fare lurking in the middle. In particular a B add on that route can go beyond £600, round trip.