Let's work on the facts........
UK APD (air passenger duty) is £65 for a flight in economy to the USA.
It is £130.00 for any other travel class (WT+, CW, F)
The additional charge between WT+ and CW is also not related to any other government / federal tax, user fee, etc etc.
It is purely British Airways surcharging, what ever they decide to call it.
The only difference to costs that I can work out is that in Club you can take an extra suitcase, and perhaps an extra bag @ 23kgs "costs" £60.00 each way to handle / fuel etc?