Tier point question

Something I have pondered for a while now.
Normally BA give 10TP for a short haul economy flight. However, from time to time I do get rewarded with 20TP. There seems to be no logic and looking back at my TP history this has happened MAN-LHR, LHR-BCN, LHR-BSL, AMS-LHR and LHR to BUD. I normally get 10TP on all these routes but have also (rarely) been awarded 20TP
Anyone any ideas why this happens?

Any flight in Y,B or H in economy (and some others such as J on domestic which is still economy) will get you 20TP’s each way.

If anyone books a lot of domestic add-ons to LHR to connect onwards then any good agent will book domestic in B Class to get clients the extra TP’s where onwards class is much lower (such as V or N).

A different and slightly unrelated TP question. Mrs Swindoneric and I are heading to the US later this year and plan to fly between Washington DC, Boston, and NY. Obviously I’ve been looking at air fares and I noticed that US Air is offering $190 for domestic first class. I am BA Silver so don’t need the free baggage and I’m not sure if I would pay the extra $90 compared to coach for 2:2 seats as opposed to 3:3. But I wondered how many tier points? From what I can see, it’s 210 provided I book before 28 April. Can’t be correct, surely? Or is it?

@Seasonedtraveller – thanks for this. Very helpful. They are simply direct flights from IAD to Bos to NYC so 120 points. Not bad for $380.
Thanks again.