To be more accurate, Balpa in BA costs 0.6% after tax relief on the subs and that is easily paid out of the latest pay rise package esp with the retention of increments & the pay scales for new entrants. So with BA recruiting I'd recommend joining Balpa to allow them to continue protect your Ts&Cs, Hotac, Rostering, Scheduling, and bonuses.
Not sure if I am allowed to publish today's offer but I'll support it.