That's because the 4 coupon pass is valid only for 6 months from issue date, whereas the 8 and 12 coupon book currently has unlimited validity - basically more flexibility. But yes, I agree with you, that if I know I'm going to travel 8 sectors within 6 months, makes much more sense to get 2x4 coupon booklets. But I'm told that the possibility of a last-minute complimentary upgrade at the airport / gate is higher if you have an 8 coupon booklet...anyone with experience on this?